Sorption cooling devices

ABSTRACT

Novel sorption cooling devices capable of providing cooling over an extended period of time are disclosed. The sorption cooling devices are particularly useful for temperature-controlled shipping containers that are required to maintain a temperature below ambient for a time sufficient to complete delivery of the container and its contents. The shipping containers can be utilized to cost-effectively transport temperature-sensitive products.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser.No. 09/876,841 filed Jun. 6, 2001 and U.S. patent application Ser. No.09/970,094 filed Oct. 2, 2001. Each of these U.S. Patent Applications isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is directed to improved sorption coolingdevices and methods for using sorption cooling devices. In particular,the present invention is directed to sorption cooling devices that areparticularly adapted to maintain a reduced temperature within anenclosed container for an extended period of time. The cooling devicesare particularly useful for temperature-controlled shipping containersthat must maintain a temperature below ambient for extended timeperiods, such as. from 1 hour to about 120 hours, or more.

[0004] 2. Description of Related Art

[0005] The shipment of products that must have their temperaturemaintained within a specific range below ambient is one of the fastestgrowing market segments in the modern shipping industry. This growth isdriven by a number of factors including widespread concerns about safetyin the cold food distribution chain, increasing numbers ofpharmaceutical and life sciences products which must have theirtemperature maintained within certain limits, the rapid growth inhigh-value specialty chemicals such as those used in the semiconductorindustry, the increasing number of sophisticated medical tests whichrequire the shipment of patient specimens to an external laboratory, theincreased number of clinical trials associated with new pharmaceuticaldiscovery and the increased delivery of products directly to thecustomer as a result of Internet ordering.

[0006] This field is generally referred to as controlled temperaturepackaging (CTP). CTP can be segmented by the target temperature range,namely: frozen (below 0° C.); 20° to 8° C.; and less than ambient (e.g.,less than 30° C.). In addition, CTP may be segmented by container size,namely: greater than pallet; one cubic foot to pallet; and less than onecubic foot. Containers having a size greater than pallet are typicallycooled by mechanical refrigeration and the shipment times are typicallyfrom days to many weeks. The one cubic foot to pallet size segment isdominated by systems using ice (e.g., gel packs) and/or dry ice as acoolant wherein the containers are insulated using expanded polystyrene(EPS). The market segment for containers less than one cubic foot insize is very limited due to an unmet need for a small, lightweightcooling mechanism.

[0007] Although many basic ice/EPS systems are in use, there is a widevariation in quality and performance of the packaging depending on thevalue of the product and the sensitivity of the product to temperaturefluctuation. A relatively simple system includes a cardboard box intowhich EPS sheets have been cut and placed. The Gontainer is then filledwith dry ice in which, for example, frozen fish is shipped. A moresophisticated approach is a validated system consisting of custom moldedEPS forms in a rigid box with both frozen and warm gel packs, thecombination of which has been tested through a range of temperaturecycles for specified thermal properties. Such a validated system can beused for shipping pharmaceuticals. For example, many pharmaceuticalproducts such as vaccines and antibodies must be maintained within arange of 2° C. to 8° C.

[0008] The existing ice/EPS cooling system is unsatisfactory for variousreasons including: increased environmental concerns associated with thedisposal of large quantities of EPS and gel packs; the high cost ofshipping; and the required freezers at the shipping source to maintainthe frozen packs. The high cost of shipping is directly related to thehigh volume associated with the EPS and the high volume and massassociated with the gel packs. For a one cubic foot box with a 60 hourlifetime at 2° C. to 8° C., over 90 percent of the volume is consumed byEPS and gel packs. Some reduction in volume and shipping costs may beobtained by using vacuum insulation panels (VIPs), but the high cost ofVIPs has precluded significant market penetration.

[0009] An example of the foregoing system is illustrated in U.S. Pat.No. 5,924,302 by Derifield issued on Jul. 20, 1999. This patentillustrates a shipping container that includes a plurality of cavitiesadapted to receive a coolant (e.g., gel packs) that surround a cavityadapted to receive an item to be shipped.

[0010] Electrically cooled shipping containers are illustrated in U.S.Pat. No. 6,192,703 by Salyer et al., issued on Feb. 27, 2001. Thispatent discloses a portable refrigerator unit and storage containeremploying vacuum insulation panels and a phase change material. Phasechange materials undergo a change in physical form (e.g., solid toliquid) thereby absorbing heat from the surrounding environment. Abattery driven refrigeration system provides cooling of the shippingcontainer.

[0011] The use of reactor-based rechargeable portable coolers areillustrated in U.S. Pat. No. 5,186,020 by Rockenfeller et al., issued onFeb. 16, 1993. This patent discloses a portable cooler utilizing agas-liquid-gas phase change to effect cooling of chamber. However, thereactor-based apparatus disclosed by Rockenfeller et al. requires asource of electricity to effect the initial gas-liquid phase change. Asa result, the apparatus occupies additional space and has additionalweight, making it cost-ineffective and severely impairing its utilityeither for a single-use basis or for a shipping container.

[0012] A sorption cooler is illustrated in U.S. Pat. No. 5,048,301 bySabin et al. This patent discloses a sorption cooling unit where thecooling liquid is maintained in the evaporator prior to the sorptionprocess. A disadvantage of this device is that too much energy isconsumed by having to cool the cooling liquid in the evaporator uponactivation of the sorption unit. Space is also wasted in that theevaporator will require a relatively large volume to enable an efficientevaporation process because both the. liquid and evaporation volume arelocated in the same general space. Furthermore, space limitationsrestrict the amount of cooling liquid that may be maintained in theevaporator.

[0013] Thus, there is a need for a temperature-controlled container,such as a shipping container, having a lightweight cooling device thatdoes not occupy a large volume. It would also be advantageous if thetemperature of the container was controllable over a range oftemperatures. It would also be advantageous if the cooling device hadthe ability to maintain the reduced temperature for an extended periodof time. It would also be advantageous if the cooling device could beused cost effectively on a single-use basis.

SUMMARY OF THE INVENTION

[0014] The present invention is directed to sorption cooling devices andtemperature-controlled containers incorporating sorption coolingdevices, particularly temperature-controlled shipping containers for thetransportation of temperature sensitive products.

[0015] The sorption cooling devices according to the present inventionprovide numerous advantages over sorption cooling devices utilized inthe prior art. According to one embodiment, a sorption cooling deviceincludes a liquid supply apparatus that is responsive to changes in theambient temperature. The apparatus includes a rigid housing, a firstflexible pouch disposed within the rigid housing that contains a highvapor pressure substance, a second flexible pouch enclosing a supplyliquid and disposed within the rigid housing adjacent to the firstflexible pouch and a liquid conduit for providing liquid communicationbetween the second pouch and an evaporator. The high vapor pressuresubstance causes the first flexible pouch to exert pressure on thesecond flexible pouch and assist in the flow of liquid from secondflexible pouch to the liquid conduit. Increases in temperature increasethe vapor pressure within the first flexible pouch, thereby increasingthe flow rate of the liquid and the cooling rate.

[0016] According to another embodiment, a sorption cooling device isprovided that includes absorber, and evaporator, a vapor passagewaydisposed between the evaporator and absorber to direct vapor from theevaporator to the absorber and a reservoir adapted to supply refrigerantliquid to the evaporator. The reservoir includes a rigid housing, afirst flexible pouch disposed within the rigid housing and enclosing ahigh vapor pressure substance, a second flexible pouch disposed withinthe rigid housing and adjacent to the first flexible pouch that enclosesa refrigerant liquid and a liquid conduit for providing liquidcommunication between the second flexible pouch and the evaporator. Thehigh vapor pressure substance causes the first flexible pouch to exertpressure on the second flexible pouch to assist in the flow ofrefrigerant liquid from the second flexible pouch to the liquid conduit.

[0017] According to another embodiment of the present invention, asorption cooling device is provided including an evaporator, an absorberadapted to absorb vapor from the evaporator, a first reservoir adaptedto contain a first refrigerant liquid, a second reservoir adapted tocontain a second refrigerant liquid, means for supplying liquid from thefirst reservoir to the evaporator at a first liquid flow rate and meansfor supplying liquid from the second reservoir to the evaporator at asecond liquid flow rate, wherein the first liquid flow rate is fasterthan the second liquid flow rate. The first reservoir can quicklyprovide the evaporator with refrigerant liquid to initiate cooling whilethe second reservoir maintains the cooling over an extended period oftime.

[0018] According to yet another embodiment of the present invention, amethod for operating a sorption cooling device is provided. The sorptioncooling device includes an evaporator and absorber. A first portion ofliquid is provided to the evaporator and a first liquid supply rate anda second portion of liquid is provided to the evaporator at a secondliquid supply rate that is lower than the first liquid supply rate. Thisenables the sorption cooling device to rapidly cool during an initialstage and maintain cooling over an extended period of time.

[0019] According to another embodiment of the present invention, asorption cooling device is provided that includes an evaporator forproviding cooling, absorber adapted to absorb vapor formed in theevaporator, at least first reservoir adapted to contain a refrigerantliquid and supply the refrigerant liquid to the evaporator, arefrigerant liquid disposed in the first reservoir and a flowrestriction device disposed between the refrigerant liquid and theevaporator to restrict flow of refrigerant liquid to the evaporator. Byrestricting the flow of liquid to the evaporator, the cooling providedby the sorption cooling device can be extended over a long period oftime.

[0020] According to another embodiment of the present invention, asorption cooling device is provided that includes an evaporator forproviding cooling, absorber adapted to absorb vapor formed in theevaporator, a liquid reservoir adapted to contain a refrigerant liquidand supply the liquid to the evaporator and a freezing point suppressionagent within the evaporator that is adapted to lower the freezing pointof the refrigerant liquid when the refrigerant liquid is fed to theevaporator. Examples of useful freezing point suppression agents includesalts sodium chloride, calcium chloride and similar salts.

[0021] According to another embodiment of the present invention, asorption cooling device is provided that includes an evaporator forproviding cooling, an absorber adapted to absorb vapor formed in theevaporator and vapor passageway adapted to permit vapor flow from theevaporator to the absorber. The vapor passageway includes a thermallyinsulating material heading a thermal resistance of at least about 2.8K.m²NV. Accordingly, heat generated in the absorber is thermallyisolated from the evaporator, enhancing the cooling capability of thesorption cooling device.

[0022] According to another embodiment of the present invention, asorption cooling device is provided including an evaporator having acooling surface, an absorber adapted to absorb vapor formed in theevaporator and a vapor passageway disposed between the evaporator andabsorber. The absorber includes a desiccant and a thermally conductivematerial disposed within the desiccant, wherein the thermally conductivematerial has a higher thermal conductivity than the desiccant. Thehigher thermal conductivity material enhances the ability of theabsorber to transfer heat away from the evaporator, thereby enhancingthe cooling ability of the sorption cooling device.

[0023] The present invention is also directed to temperature-controlledcontainers incorporating sorption cooling devices, such astemperature-controlled shipping containers. According to one embodiment,a temperature controlled container is provided that includes a bottomcontainer portion having a bottom wall in at least a first sidewalldefining a cavity adapted to contain a product therein. A top containerportion includes a top surface and a bottom surface and is adapted tocombine with a bottom container portion to define a product cavity, thetop container portion forming the top wall of the container. A sorptioncooling device is disposed in the top portion wherein the coolingsurface of the evaporator is adapted to provide cooling to the productcavity.

[0024] According to another embodiment of the present inventions atemperature-controlled shipping container is provided that includes atleast a sidewall and top and bottom walls defining a cavity adapted tocontain a product within the cavity. A sorption cooling device isincorporated in the container that is adapted to cool the cavity. Thesorption cooling device includes an evaporator in thermal communicationwith the cavity, an absorber adapted to absorb vapor formed in theevaporator, a vapor passageway disposed between the absorber andevaporator and a reservoir adapted supply refrigerant liquid to theevaporator wherein a vapor pressure within the reservoir causes the flowrate of refrigerant liquid to increase in response to an increase inambient temperature. The reservoir can include a rigid housing, a firstflexible pouch disposed within the rigid housing and enclosing highvapor pressure substance within the first flexible pouch and a secondflexible pouch disposed within the rigid housing adjacent to the firstflexible pouch and enclosing a refrigerant liquid. A liquid conduit isprovided for liquid communication between second flexible pouch and theevaporator. The high vapor pressure substance causes the first flexiblepouch to exert pressure on the second flexible pouch to assist the flowof refrigerant liquid to the liquid conduit.

[0025] According to another embodiment, a temperature controlledcontainer is provided that includes a container heading at least asidewall and top and bottom walls defining a cavity adapted to contain aproduct therein, the sorption cooling device having an evaporator, anabsorber and a vapor passageway disposed between the evaporator and theabsorber wherein the evaporator is disposed in thermal communicationwith the cavity to provide cooling to the cavity and a liquid reservoiradapted to provide liquid to the evaporator upon activation of thesorption cooling device.

[0026] According to another embodiment, a temperature-controlledshipping container is provided that includes an insert having top,bottom and sidewalls defining a cavity within the insert and a sorptioncooling unit incorporated in the insert wherein the sorption coolingunit includes an evaporator positioned adjacent to the cavity to providecooling to cavity. A container substantially encloses the insert.

[0027] According to another embodiment of the present invention, atemperature controlled shipping container is provided that includes acontainer having at least sidewall and top and bottom walls defining acavity that is adapted to contain a product therein. A sorption coolingdevice is incorporated in the temperature-controlled shipping containerthat includes a liquid reservoir, an evaporator in thermal communicationwith the cavity to provide cooling to the cavity, an absorber which isthermally isolated from the cavity and means for supplying liquid fromthe reservoir to the evaporator upon activation of the device.

[0028] The present invention also provides a method for transporting aproduct that requires cooling. The method includes the steps ofplacing.the product within a product cavity defined by at least top andbottom walls, placing a sorption cooling device in thermal communicationwith the cavity whereby the sorption cooling device is adapted to coolthe cavity upon activation of the device, activating the sorptioncooling device to initiate cooling of the cavity, transporting theproduct contained in the cavity from a first location to second locationand removing the product from the cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIGS. 1 and 2 illustrate a cross-sectional view of a sorptioncooling device in accordance with an embodiment of the presentinvention.

[0030]FIG. 3 illustrates an exploded view of a sorption cooling devicein accordance with an embodiment of the present invention.

[0031]FIGS. 4a-4 c illustrate various cross-sectional views of liquidreservoir systems for a sorption cooling device in accordance with anembodiment of the present invention.

[0032]FIG. 5 illustrates the vapor pressure of water as a function oftemperature.

[0033]FIGS. 6 and 7 illustrate cross-sectional views of a liquidreservoir system for a sorption cooling device in accordance with anembodiment of the present invention.

[0034]FIG. 8 illustrates a perspective view of a liquid reservoir systemfor a sorption cooling device in accordance with an embodiment of thepresent invention.

[0035]FIG. 9 illustrates the variation in heat load and liquid feed rateas a function of ambient temperature.

[0036]FIG. 10 illustrates a multi-stage liquid delivery system that isuseful in a sorption cooling device in accordance with an embodiment ofthe present invention.

[0037]FIG. 11 illustrates a flow restriction device that is useful in asorption cooling device in accordance with an embodiment of the presentinvention.

[0038]FIG. 12 illustrates a flow restriction device that is useful in asorption cooling device in accordance with an embodiment of the presentinvention.

[0039]FIG. 13 illustrates a perspective view of a vapor passagewayelement that is useful in a sorption cooling device in accordance withan embodiment of the present invention.

[0040]FIG. 14 illustrates a perspective view of a vapor passagewayelement that is useful in a sorption cooling device in accordance withan embodiment of the present invention.

[0041]FIG. 15 illustrates the absorption capacity of two differentdesiccants that are useful in accordance with the present invention.

[0042]FIG. 16 illustrates a cross-sectional--view of anabsorber-including a desiccant and a high thermal conductivity materialaccording to an embodiment of the present invention.

[0043]FIG. 17 illustrates a cross-sectional view of an absorberincluding a desiccant and a high thermal conductivity material accordingto an embodiment of the present invention.

[0044]FIG. 18 illustrates the absorption capacity of a desiccant as afunction of vapor pressure at three different temperatures.

[0045]FIG. 19 illustrates a cross-sectional view of a multiple-stagesorption cooling device according to an embodiment of the presentinvention.

[0046]FIG. 20 illustrates a cross-sectional view of atemperature-controlled shipping container in accordance with anembodiment of the present invention.

[0047]FIG. 21 illustrates a cross-sectional view of atemperature-controlled shipping container in accordance with anembodiment of the present invention.

[0048]FIG. 22 illustrates a perspective view of a temperature-controlledshipping container in accordance with an embodiment of the presentinvention.

[0049]FIG. 23 illustrates a perspective view of a sorption coolingdevice in accordance with an embodiment of the present invention.

[0050]FIG. 24 illustrates a cross-sectional view of atemperature-controlled shipping container in accordance with anembodiment of the present invention utilizing multiple cooling devices.

[0051]FIG. 25 illustrates a perspective view of a temperature-controlledshipping container in accordance with an embodiment of the presentinvention.

[0052]FIG. 26 illustrates a perspective view of a temperature-controlledshipping container in accordance with an embodiment of the presentinvention utilizing multiple cooling devices.

[0053]FIG. 27 illustrates a perspective view of a sorption coolingdevice in accordance with an embodiment of the present inventiondisposed in a cylindrical shipping container.

[0054]FIG. 28 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0055]FIG. 29 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0056]FIG. 30 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0057]FIG. 31 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance.with an embodiment of the present invention.

[0058]FIG. 32 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0059]FIG. 33 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0060]FIG. 34 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0061]FIG. 35 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0062]FIG. 36 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0063]FIG. 37 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0064]FIG. 38 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0065]FIG. 39 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0066]FIG. 40 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0067]FIG. 41 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0068]FIG. 42 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0069]FIG. 43 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0070]FIG. 44 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0071]FIG. 45 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0072]FIG. 46 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0073]FIG. 47 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0074]FIG. 48 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

[0075]FIG. 49 illustrates the temperature of the desiccant and internalcavity of a temperature-controlled shipping container as a function oftime in accordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

[0076] The present invention is generally directed to sorption coolingdevices and, in a particularly preferred embodiment, is directed totemperature-controlled containers incorporating one or more sorptioncooling devices that enable the internal cavity of the container to bemaintained at a reduced temperature. Such containers are particularlyuseful as shipping containers for the transport of a variety of goodsthat are sensitive to ambient temperature conditions.

[0077] When the sorption cooling device is incorporated into a shippingcontainer, the goods to be transported can be placed within a productcavity that is defined by the shipping container. The shipping containercan be in the form of a traditional box, a cylindrical tube, a shippingenvelope or virtually any other form that is useful for transportinggoods. The sorption cooling devices of the present invention eriable awide range of container sizes to be used from very small (e.g., down toseveral cubic inches) up to pallet size (e.g., to over 100 cubic feet).The sorption cooling device is then placed in thermal communication withthe product cavity to provide cooling to the goods contained within thecavity. . The device can be activated prior to placement near theproduct cavity or at some time after placement. Cooling can continue ina well-controlled manner to maintain the desired temperature (e.g., notgreater than about 8° C.) for an extended time period of up to about 120hours or more, such as from about 24 to about 72 hours, to enable thegoods to arrive at their destination without being subjected totemperatures in excess of a desired maximum temperature.

[0078] The fundamental operation of a sorption cooling device is wellknown. The boiling point of a liquid can be lowered by reducing thepressure over the liquid, such as by placing the liquid in a vacuum. Aliquid, for example water, that is under a substantially reducedpressure will boil and absorb heat from the surrounding environment.This absorption of heat creates the desired cooling affect. To preventthe development of high vapor pressure over the boiling liquid, whichwould stop the boiling of the liquid, the vapor that is generated mustbe continuously removed and the removal of the vapor must be donewithout the introduction of outside air. Thus, an absorptive material,such as a desiccant, can be utilized to absorb the vapor and permit theliquid to continue boiling and absorbing heat from the environment. Anexample of a sorption cooling device is described in U.S. Pat. No.4,250,720 by Siegel, which is incorporated herein by reference in itsentirety.

[0079] The sorption cooling device that is utilized for thetemperature-controlled shipping container according to the presentinvention can have a variety of configurations. Preferred sorptioncooling devices are relatively lightweight and do not occupy a largevolume, leading to high cooling densities. FIGS. 1 and 2 illustrate across-sectional view of one such sorption cooling device that ispreferred in accordance with an embodiment of the present invention andFIG. 3 illustrates an exploded view of the same cooling device. It willbe appreciated that the physical dimensions of the various componentsillustrated in the Figures are not drawn to scale. The sorption coolingdevice 100 includes an absorber 102 containing an absorptive materialsuch as desiccant 118 and an evaporator 108 that includes a coolingsurface 120. A vapor passageway 104 is disposed between the evaporator108 and absorber 102 to provide vapor communication between theevaporator 108 and absorber 102. The vapor passageway 104 includes athermally insulative material 122 disposed between the evaporator 108and absorber 102 and a plurality of apertures 114 through the thermallyinsulative material for vapor communication. A vapor permeable membrane106 is disposed between the evaporator 108 and the vapor passageway 104.A liquid reservoir 110 containing a refrigerant liquid 116 is connectedto the evaporator 108 by a liquid conduit 112. A flow restriction 124can be disposed between the liquid 116 and the evaporator 108, such asin the liquid conduit 112.

[0080] Referring to FIG. 2, upon activation of the device 100, at leasta portion of the refrigerant liquid 116 exits the liquid reservoir 110and passes to the evaporator 108 by means of the liquid conduit 112. Asthe liquid 116 enters the evaporator 108, it will evaporate due toreduced pressure thereby causing the evaporator to take in heat from itssurroundings at the cooling surface 120. The vapor formed in theevaporator 108 passes through the vapor permeable membrane 106, throughthe apertures 114 and is absorbed into the absorber 102. The vapor isabsorbed by the desiccant 118 in the absorber 102 thereby causing heatto be generated in an amount greater than that taken in by theevaporator 108. The thermally insulative material 122 reduces the amountof heat that is transferred back to the evaporator 108 from the absorber102.

[0081] In order for the liquid to boil in the evaporator 108, thesorption cooling device 100 is enclosed in an airtight enclosure (notillustrated) at a reduced internal pressure and preferably is maintainedunder a substantial vacuum. More particularly, the pressure within theenclosure surrounding the cooling device (i.e., the evaporator andabsorber) Is preferably not greater than about 20 mbar (15 torr), morepreferably not greater than about 10 mbar (7.5 torr) and even morepreferably not greater than about 4 mbar (3 torr) As is discussed inmore detail below, the liquid reservoir 110 can be maintained at ahigher pressure than the remainder of the sorption cooling device. Tomaintain the reduced pressure and to provide an adequate shelf life forthe device, the sorption cooling device 100 is preferably enclosed in animpermeable casing material such as a metallized polyester film toprevent the leakage of gases into the device. In one embodiment, thesorption cooling device 100 is disposed in a semi-rigid,thermally-formed plastic tray and a metallized film is adhered to thetop surface of the plastic tray to enclose the cooling device within thetray which is evacuated to a reduced pressure.

[0082] In operation, the liquid reservoir 110 is activated to releasethe liquid 116 to the evaporator 108. The liquid reservoir can have ahigher pressure than the remainder of the cooling device to feed theliquid to the evaporator 108. For example, the liquid reservoir 110 canbe a simple polymeric pouch exposed to ambient pressure that ispunctured to release the liquid 116. Alternatively, a valving mechanismcan be used to expose the liquid 116 to reduced pressure in theevaporator 108. In either case, the liquid is exposed to the evaporator108 and is thereby exposed to a substantial drop in pressure causing theliquid to flow to the evaporator 108 and vaporize.

[0083] The temperature-controlled shipping containers in accordance withthe present invention require that the product be cooled for an extendedperiod of time, such as from 1 hour to 120 hours, to provide asufficient amount of time for the product to reach its destination. Toprovide adequate cooling over a long period of time, there must eitherbe a large quantity of refrigerant liquid initially present in theevaporator or additional liquid must be added to the evaporator over aperiod of time. If all of the liquid is stored in the evaporator (e.g.,without a separate reservoir), then the entire volume of liquid must becooled before the device can provide external cooling. Furthermore,there is a practical limit to the amount of liquid that can be stored inthe evaporator. It is preferable for these and other reasons accordingto the present invention to maintain the liquid in a remote location(e.g., reservoir 110) and distribute the liquid to the evaporator in acontrolled fashion and enable the sorption cooing device to providecooling for an extended period of time.

[0084] The liquid feed rate from the liquid reservoir to the evaporatorwill be proportional to the pressure difference between the totalpressure in the reservoir (i.e., the water vapor pressure plus theresidual air pressure) and the pressure in the evaporator (i.e., watervapor pressure at the evaporator temperature and the residual airpressure after evacuation). To initiate a faster liquid feed rate whenthe sorption cooling device is first activated, a small amount ofresidual pressure can be incorporated in the reservoir. For example, theinitial pressure in the reservoir housing can be from about 4 mbar (3torr) to about 700 mbar (525 torr) and preferably is not greater thanabout 700 mbar (525 torr). When residual pressure is used, the totalpressure in the reservoir will rapidly decrease as the liquid flows fromthe reservoir to the evaporator, decreasing the feed rate and therebydecreasing the cooling rate. This residual pressure is useful toinitially bring the contents of a product cavity down to the desiredtemperature in a short period of time.

[0085] It will be appreciated that the liquid reservoir 110 can belocated at virtually any position in relation to the remainder of thesorption cooling device, as long as fluid communication is provided fromthe reservoir 110 to the evaporator 108. According to one embodiment ofthe present invention, the reservoir is separated from the evaporator108 by the thermally insulative material 122 and that the liquidreservoir 110 is disposed adjacent to the absorber 102. For example, theliquid reservoir 110 can be disposed adjacent to the absorber 102 insuch a manner that the top of the liquid reservoir 110 and the top ofthe absorber 102 are substantially planar, creating a substantially flattop surface for the cooling device, as is illustrated in FIGS. 1 and 2.This configuration can simplify the incorporation of the device into acontainer having a flat external surface. In some instances it is notdesired or required that all the liquid be supplied immediately or in anuncontrolled fashion to the evaporator. To restrict liquid flow betweenthe evaporator 108 and liquid reservoir 110, a flow restriction device124, as is discussed in more detail below, may be incorporated betweenthe liquid. 116 and the evaporator 108.

[0086] According to one embodiment of the present invention, the liquidreservoir is constructed such that the liquid feed rate from thereservoir to the evaporator varies automatically in response to changesin the ambient temperature. As a result, the cooling rate of thesorption cooling device also varies in response to changes in theambient temperature. According to this embodiment, the refrigerantliquid is contained in a rigid housing and vapor pressure within therigid housing drives and controls the liquid feed rate. When thereservoir is exposed to ambient conditions, small changes in the ambienttemperature can produce a change in the vapor pressure, leading to asignificant change in the liquid feed rate and therefore a change in thecooling rate. As used herein, the term ambient refers to the conditions(e.g., the temperature or pressure) surrounding the cooling device orsurrounding the container into which the cooling device is incorporated.

[0087] According to this embodiment, a vapor pressure within a rigidhousing and isolated from the ambient pressure conditions is used as adriving force for the liquid, as opposed to ambient pressure.Preferably, at least a portion of the reservoir is in thermalcommunication with the ambient environment so that the vapor pressurewithin the rigid housing will rise and fall with fluctuations in theambient temperature. Further, the reservoir should be thermally isolatedfrom the evaporator. To prevent ambient pressure from influencing thefeed rate, the reservoir housing is sufficiently rigid to maintain thepressure difference between the interior and exterior of the housing.For example, the liquid can be contained directly within the rigidhousing such that it is free to move about the internal cavity of thehousing. As the ambient temperature increases, the temperature of thereservoir will increase and the vapor pressure over the liquid willincrease, thereby causing the hydrostatic head pressure of the liquid toincrease.

[0088]FIG. 4a illustrates an example of this embodiment according to thepresent invention. The liquid supply reservoir 400 a includes a rigidhousing 402 a with a refrigerant liquid 404 a disposed within the rigidhousing 402 a. An outlet 406 a connects the liquid reservoir 400 a to aliquid conduit 408 a which includes a flow restriction device 410 a. Therefrigerant liquid 404 a has a vapor pressure that exerts pressure 412 aon the liquid to influence the liquid flow rate out of the reservoir 400a.

[0089] The change in vapor pressure associated with a change in thetemperature of the reservoir can be quite significant. For example, FIG.5 illustrates the change in water vapor pressure as a function oftemperature up to about 30° C. As is evident from FIG. 5, the watervapor pressure changes significantly (about 800%) with an increase intemperature in the range of 0° C. to 30° C. Therefore, if the rigidhousing is exposed to fluctuations in the ambient temperature, the vaporpressure will increase and the feed 2-5 rate of the liquid willincrease, thereby increasing the cooling rate.

[0090] However, in a design such as that illustrated by FIG. 4a, it ispossible that certain orientations of the reservoir will cause theliquid to become separated from the liquid conduit, temporarilysuspending the flow of liquid. To overcome this limitation, the liquidcan be contained within a wicking material disposed in the housing thatmaintains some of the liquid in contact with the outlet irrespective ofthe orientation of the reservoir. In another embodiment, the liquid iscontained in a flexible, liquid impermeable pouch to maintain liquidcommunication with the liquid conduit.

[0091] Referring to FIG. 4b, an embodiment is illustrated wherein aliquid impermeable pouch 414 b encloses the refrigerant liquid 404 b.The residual vapor pressure 412 b acts upon the liquid pouch 414 b,which is preferably a flexible pouch to enable the vapor pressure to betransmitted to the liquid contained within the pouch. It will beappreciated that the residual vapor pressure within the rigid housingcan be supplied by a substance that is different than the refrigerantliquid 404 b, such as a substance having a higher vapor pressure thanthe refrigerant liquid. FIG. 4c illustrates an embodiment wherein awicking material 416 c is disposed within the rigid housing 402 c. Therefrigerant liquid 404 c is absorbed into the wicking material 416 c andas a result maintains contact with the liquid outlet 406 c irrespectiveof the orientation of the reservoir 400 c. Examples of a wickingmaterial useful for this purpose include fibrous woven and nonwovenmaterials such as those comprising natural fibers (e.g. cellulose),polymers, glass (e.g. silica), natural sponges and synthetic sponges.

[0092] In one preferred embodiment, the vapor pressure of a separate,high vapor pressure substance is used to drive the feed rate of theliquid to the outlet. In this embodiment, a first flexible pouchcontaining a high vapor pressure substance located adjacent to a secondflexible pouch containing a liquid. As the ambient temperature increase,the vapor pressure within the first pouch will also increase therebycausing the first pouch to expand. As the first pouch expands, it exertsincreased pressure on the second pouch thereby increasing the pressureof the liquid over the liquid outlet. FIGS. 6 and 7 illustratecross-sectional views of a liquid supply reservoir in accordance withthis embodiment of the invention and FIG. 8 illustrates a perspectiveview of this liquid supply reservoir. Specifically, FIG. 6 illustrates across-section of the reservoir prior to activation of the device andFIG. 7 illustrates a cross-section of the reservoir illustrated in FIG.6, wherein the device has been activated and some liquid has beenreleased from the second pouch.

[0093] The liquid supply reservoir 600 includes a first flexible pouch602 containing a high vapor pressure substance 606, a second flexiblepouch. 604 containing a supply liquid 608 such as a refrigerant liquid,and a liquid outlet 610 connected to a liquid conduit 612. The firstpouch 602 and second pouch 604 are adjacent and generally encased by arigid housing 614 such that the first pouch 602 may not expand in anydirection other than a direction that is substantially toward the secondpouch 604. Upon activation, the liquid 608 flows to the liquid outlet610, at least partially due to the pressure exerted by the first pouch602. The high vapor pressure substance 606 can advantageously have ahigher vapor pressure than that of the liquid 608 at near ambienttemperatures (e.g., about 30° C.). As such, as the ambient temperatureincreases so will the vapor pressure of the high vapor pressuresubstance 606 thereby causing the first pouch 602 to expand. As thefirst pouch 602 expands it will cause the second pouch 604 to contractthereby assisting the flow of the liquid 608 from the second pouch tothe liquid conduit 612. The flexible pouches can be made from any numberof flexible, liquid impermeable materials, including low-cost,heat-sealed films such as polypropylenes, polyesters, nylons or otherplastics. A flow restriction device 616, may be incorporated in theliquid conduit 612 to restrict the liquid flow rate to an appropriatelevel.

[0094] Preferably, the pressure in the second pouch 604 immediatelyprior to activation of the device is greater than the pressure withinthe rigid housing 614. This will prevent the pressure within the rigidhousing 614 from exerting itself on the second pouch upon activation,which would thereby cause the liquid to exit the liquid conduit at anincreased rate. For example, the pressure within the second pouchimmediately prior to activating the device can be from about 50 mbar(37.5 torr) to about 300 mbar (225 torr) and the pressure within therigid housing is preferably not greater than about 700 mbar (525 torr),such as not greater than about 100 mbar (75 torr) and not greater thanabout 10 mbar (7.5 torr).

[0095] Moreover, the pressure within the rigid housing should not begreater than the pressure within the first pouch at ambient temperaturesand will typically be at the same pressure as the cooling device, i.e.,most preferably not greater than about 4 mbar (3 torr). This will allowthe first pouch to expand within the rigid housing without beingrestricted by the influence of surrounding pressure. If the pressurewithin the rigid housing is greater than the pressure within the firstpouch, the first pouch will not be able to expand and exert pressure onthe second pouch. As a result, it is preferred that the pressure withinthe first pouch be greater than the pressure within the rigid housing.More preferably, the pressure within the first pouch is at least about100 mbar (75 torr), and more preferably is at least about 500 mbar (375torr) higher than the pressure within the rigid housing.

[0096] According to the present invention, the rigid housing issufficiently rigid and gas impermeable such that the ambient pressureexerted on the housing is not substantially transferred to the liquid inthe second pouch. For example, the rigid housing can be fabricated froma metal or a plastic such as polyethylene, polypropylene, polyvinylchloride, or similar materials. Furthermore, to ensure that changes inthe ambient temperature rapidly change the temperature and the vaporpressure within the rigid housing, the rigid housing is at leastpartially in thermal communication with ambient temperature andpreferably has a thermal conductivity of at least about 0.2 W/m.K. Thereservoir shouid also be thermally isolated from the cooling surface ofthe evaporator so that the evaporator does not influence the temperatureof the high vapor pressure substance. One of the walls of the rigidhousing adjacent to the first pouch can also be constructed of a higherthermal conductivity material to increase the internal temperature ofthe first pouch more rapidly. Accordingly, an increase in the ambienttemperature will cause the high vapor pressure substance to increase intemperature, increasing the vapor pressure and increasing the flow rateof the liquid to the liquid conduit.

[0097] The high vapor pressure substance can be any suitable liquid orgas phase material that experiences a relatively high change in itsvapor pressure over a temperature range of from about 20° C. to about55° C. Preferably, the vapor pressure of the high vapor pressuresubstance will increase by at least about 600 percent (i.e., 6 times)with a temperature change of from 20° C. to 55° C. Such high vaporpressure substances can include alcohols such as ethanol, methanol andisopropanol, and alkanes such as n-butane, isobutane, n-pentane andn-hexane. Other high vapor pressure compounds such as fluorocarbons, canalso be used. Fluorocarbon compounds can include chlorofluorocarbons(CFC) or hydrochlorofluorocarbons (HCFC) such as FREON (E.I. Dupont deNemours, Wilmington, Del.), a series of fluorocarbon products such asFREON C318, FREON 114, FREON 21, FREON 11, FREON 114B2, FREON 113 andFREON 112. Other useful fluorocarbons liquids include HCFC-134a,HCFC-141b and HCFC-245fa. In one preferred embodiment, the high vaporpressure substance comprises a material that is substantiallynonflammable, enabling the device to be utilized in shipping containerswithout restrictions on the mode of transportation. Such high vaporpressure substances include water. The first flexible pouch containingthe high vapor pressure substance can be readily recycled after usesince there is substantially no loss of the substance out of the pouchduring operation of the device.

[0098] The sorption cooling device in accordance with the presentinvention is particularly useful in temperature-controlled shippingcontainers. To further illustrate this embodiment of the presentinvention, a model has been developed that shows the change in waterfeed rate as a function of ambient temperature and compares it to thechange in heat load for a container with an internal temperature of 5°C.

[0099] The heat load for a container depends on the surface area of thecontainer, the temperature difference between the interior and exteriorof the container, and the overall heat transfer coefficient(U_(o)),which depends on the internal and external heat transferconstants as well as the thickness and thermal conductivity of thecontainer insulation. The total heat load (Q_(heat)) in watts can beexpressed as:

Q _(heat)(W)=U _(o)(W/m ² K)A(m ²)[T _(ambient) −T _(box)](K)   (1)

[0100] For a given container, U_(o) and A are fixed and the heat load isdirectly proportional to the temperature difference between ambient andthe internal cavity. To maintain the internal temperature at a constantvalue, the water feed rate must be sufficient to provide an equivalentamount of cooling (Q_(heat)=Q_(cool)).

[0101] The heat of vaporization of water is about 694 w·hr/g at 25° C.Thus, if the mass flow rate in g/min is expressed as m, then the coolingrate is:

Q _(cool)(W)=694W·hr/gm (g/min)60 min/hr   (2)

[0102] The magnitude of m is directly proportional to the pressure dropbetween the liquid reservoir and the evaporator.

[0103]FIG. 9 illustrates the variation in Q_(heat) for a containerinternal cavity temperature of 5° C. that has been normalized to a valueof 1 at 20° C. Also illustrated are normalized cooling rates for thevariable feed rate embodiment of the present invention and for a liquidfeed system that does not change with. temperature until freezingoccurs, which terminates water flow. As is illustrated by FIG. 9, adramatic change in feed rate with increased ambient temperature aroundthe container is obtained according to the present invention. If theresidual air pressure in both the water feed reservoir and evaporator iszero, the cooling rate is proportional to the vapor pressure differencebetween ambient temperature and the evaporator temperature. By changingthe residual air pressure.in the reservoir, the temperature dependencecan be changed significantly.

[0104] According to another embodiment of the present invention, theflow of liquid can also be controlled using a multi-stage liquiddelivery system. In this embodiment, two or more sources of liquid canbe activated simultaneously or can be activated separately to provideliquid to the evaporator. This embodiment of the present invention isuseful for supplying liquids at different flow rates, supplying liquidsat different times and supplying liquids of differing chemicalcomposition.

[0105] In one embodiment, a first starter volume of liquid can beinitially released at a rapid flow rate to saturate the evaporator whilea larger second volume of liquid is released at a reduced flow rate inorder to provide prolonged evaporation of the liquid and extend theuseful lifetime of the sorption cooling device. The first volume ofliquid will disperse throughout the evaporator so that initial coolingcan begin quickly across the entire cooling surface of the evaporator.The second liquid can then be fed to the evaporator at a controlled rateto maintain the required degree of cooling in the evaporator during theuseful lifetime of the device. The reservoirs may be entirely separatereservoirs that are activated separately or they may be incorporatedinto a single unit that can be activated by a single actuator.

[0106] In the case of separate reservoirs, a starter reservoir caninclude a volume of liquid that is contained within a liquid impermeablepouch. This pouch can be ruptured either by direct mechanical pressureor by indirect or assisted mechanical pressure by means of a mechanicallever or sharpened actuator which is either affixed to the outside ofthe pouch or integrated within the pouch. This pouch can be locatedeither directly on the evaporator surface or can be located remotelywherein a liquid conduit directs the flow of liquid to the evaporator.If the pouch is located remotely, the liquid conduit may include aliquid impermeable material that encapsulates the entire liquid pouchand an actuator and is adapted to puncture the pouch and deliver liquidto the evaporator.

[0107] One example of this embodiment of the present invention isillustrated in FIG. 10. A reservoir 1000 includes a first liquid pouch1002 disposed in a rigid housing 1004. The first liquid pouch 1002includes a first refrigerant liquid 1006. An actuator 1008 is adapted topuncture the first liquid pouch 1002 and release the first refrigerantliquid 1006. The first refrigerant liquid 1006 can then flow freely tothe liquid conduit 1010, and to the evaporator to quickly saturate awicking material disposed in the evaporator.

[0108] A second liquid pouch 1012 is also provided within.the rigidhousing 1004 and includes a second refrigerant liquid 1014. In oneembodiment, the volume of the second refrigerant liquid 1014 is greaterthan the volume of the first refrigerant liquid 1006. When the actuator1008 punctures the first liquid pouch 1002, the second refrigerantliquid 1014 is also exposed to a reduced pressure Optionally, a secondactuator could be provided to puncture the second liquid pouch 1012 andrelease the second refrigerant liquid 1014, either simultaneously withthe actuator 1008 or at some time after the release of the firstrefrigerant liquid 1006. In the embodiment illustrated in FIG. 10, thesecond refrigerant liquid 1014 flows through the first liquid pouch 1002to the liquid conduit 1010 and a flow restriction device 1016 isdisposed between the first liquid pouch 1002 and the second liquid pouch1012 to reduce the flow rate of the second refrigerant 1014.Accordingly, the second refrigerant liquid 1014 will be fed to theevaporator at a reduced flow rate and over an extended period of time.

[0109] Refrigerant liquids for use in accordance with the presentinvention should have a high vapor pressure at ambient temperature sothat a reduction of pressure will produce a high vapor production rate.For most applications, the liquid should also have a high heat ofvaporization per unit mass or volume, should be non-toxic andnonflammable and should have relatively low cost. Suitable liquidsinclude ammonia, various alcohols such as methyl alcohol or ethylalcohol, ketones (e.g., acetone) or aldehydes (e.g., acetaldehyde).Other useful liquids can include chlorofluorocarbons (CFC) orhydrochlorofluorocarbons (HCFC) such as FREON (E.I. Dupont de Nemours,Wilmington, Del.), a series of fluorocarbon products such as FREON C318,FREON 114, FREON 21, FREON 11, FREON 114B2, FREON 113 and FREON 112.Other useful fluorocarbons liquids include HCFC-134a, HCFC-141b andHCFC-245fa.

[0110] Preferably, the liquid includes water (i.e., is an aqueous-basedliquid) and in one embodiment the liquid consists essentially of water.Water is advantageous due to its high heat of vaporization, low cost andlow toxicity. However, it may be desirable to include minor amounts ofother components in the liquid in order to control the evaporativeproperties of the liquid. For example, the liquid can be mixed with acomponent having a low vapor pressure or with a gas, such as carbondioxide.

[0111] Further, additives to lower the freezing point of the water canbe used. Specifically, cooling may occur in the evaporator to such adegree that the liquid may begin to freeze within the evaporator. Thiscan result in many problems, including uneven temperature distributionand uneven distribution of the liquid. If the liquid is fed to theevaporator over a long period of time, freezing may also block the flowof additional liquid to the evaporator. In order to alleviate suchproblems, it can be advantageous to depress the freezing point of theliquid.

[0112] Freezing point depression can be accomplished by mixing afreezing point suppression agent with the liquid to lower the freezingpoint. As many of these substances will also cause a suppression invapor pressure above the liquid that is proportional to the quantityadded, it is desirable to use only the amount needed to adequatelysuppress freezing of the liquid. Other high-vapor pressure solvents maybe used to depress the freezing point, but these may interfere with thevapor flow from the evaporator to the absorber by producing higherrelative pressures between the evaporator and the absorber. Therefore,these should be used in moderation.

[0113] Preferred freezing point suppression agents according to thepresent invention include salts such as metal-chlorides, -bromides,-nitrates, -sulfates and -acetates. Examples of preferred metal saltsinclude those selected from the group consisting of NaCl, CaCl₂, BaCl₂,MgCl₂, FeCl₃, Mg(NO₃)₂, NaBr, ZnCl₂ and mixtures thereof. Other usefulfreezing point suppression agents include organic solvents such as EtOH,MeOH, IPA, ethylene glycol, propylene glycol.and glycerol.

[0114] In cases where the liquid is fed to the evaporator over a longperiod of time, mixing these freezing point suppression agents with thebulk liquid can cause an accumulation of these compounds in theevaporator. As the liquid evaporates, the compound will remain in theevaporator while additional amounts of the compound are introduced withthe in-flowing liquid.

[0115] In order to minimize this problem, the proper volumes of thefreezing point suppression agent may be introduced to the evaporatorthrough pre-impregnation of the evaporator. In this way, when newrefrigerant liquid is fed into the evaporator, it will mix with theagent in the correct proportion to reduce freezing in the evaporator.For example, a wicking material, disposed in the evaporator (discussedbelow) can be impregnated with a controlled amount of a freezing pointsuppression agent. This problem can also be minimized by adding theagent to the starter liquid only, as is discussed above. In this regard,the starter liquid can include a quantity (e.g., up to about 30 wt. %)of a salt, such as NaCl or CaCl₂, or an organic compound such asethylene glycol.

[0116] According to one embodiment of the present invention, the flowrate of the refrigerant liquid (e.g., water) from the reservoir to theevaporator is carefully controlled to regulate the overall cooling rateof the sorption cooling device. For applications such astemperature-controlled shipping containers, relatively low cooling poweris required, but the cooling must continue for long periods of time,often in excess of 48 or 72 hours. In order to provide an extendedperiod of cooling according to the present invention, a controlledliquid flow rate is maintained into the evaporator to maintain a steadylevel of cooling over a long time period. Absent proper control,substantially all of the liquid in the reservoir would immediately flowto the evaporator upon release from the reservoir. According to thepresent invention, a liquid flow restriction can be used to restrict theliquid flow rate to an appropriate level.

[0117] Referring now to FIG. 11, a cross-sectional view of a flowrestriction device that is useful in accordance with the presentinvention is illustrated. Supply reservoir 1102 includes a supply liquid1104 and a liquid outlet 1106. The liquid outlet 1106 is connected to aliquid conduit 1108 that includes a flow restriction device 1110 adaptedto restrict the flow of the supply liquid 1104 exiting the reservoir.The flow restriction device 1110 can be any type of partial barrier thatpermits liquid to flow to the evaporator but causes the flow rate of theliquid to be reduced. One useful flow restriction method is to seal oneor more lengths of capillary tubing of a pre-selected diameter into theliquid conduit 1108 in such a way as to force the liquid to flow throughthe capillary.tube. The liquid flow rates for water at 1 bar of pressureand the estimated cooling rate for different samples of capillary.tubing having a 1 cm length and a diameter ranging from 20 μm to 100 μmas are listed in Table 1. TABLE 1 Capillary Tube Properties DiameterWater Feed Rate Cooling Rate (μm) (ml/hr) (W) 20 0.17 0.11 40 2.7 1.7 6013.7 8.6 100 106 66.8

[0118] As is evident from Table 1, the flow rate and the cooling ratecan be controlled through proper selection of the capillary tubing. Thecapillary tubing can have a range of from about 1 μm diameter up toabout 1000 μm diameter.

[0119] Another means for restricting the flow rate is to increase theviscosity of the liquid. This can be accomplished by the addition ofgelling agents such as silicas, polymers and starches to the liquid.Another means for flow restriction is to use the viscosity of the liquidto reduce the flow rate as it passes through one or more restrictions inorder to maintain the proper flow rate. For example, the liquid can beforced to flow through one or more small apertures or pores. The flowrate is thereby controlled by one or more of the liquid viscosity, thediameter and length of the apertures and the pressure drop between bothsides of the device. Accordingly, a porous membrane or plug having apre-selected pore volume and pore size can be incorporated into theliquid conduit. The selected pore characteristics such as pore size willdepend upon the plug length, the driving pressure, thehydrophocity/hydrophilicity characteristics, and the like.

[0120] Alternatively, a porous membrane can be incorporated into theliquid pouch. Upon actuation, the liquid will then flow through theporous membrane in. order to exit the liquid pouch. The pore size andthickness of the membrane can be selected to provile the desired liquidflow rate based upon the cooling rate that is required for theapplication. According to one embodiment, the membrane has an averagepore size of from about 0.05 μm to about 20 μm. An example of thisembodiment of the present invention is illustrated in FIG. 12. Theliquid pouch 1200 includes a liquid impermeable outer casing 1202. Theinterior of the casing 1202 includes a porous membrane 1204 disposedsuch that the liquid 1206 must pass through the membrane 1204 beforeexiting the casing 1202. The liquid pouch 1200 can be activated torelease liquid by puncturing the casing 1202 in an outward direction.For example, an actuator having a sharpened end (not illustrated) can bedisposed between the casing 1202 and the membrane 1204 such that thesharpened end punctures the casing 1202 without puncturing the membrane1204. It will be appreciated that the membrane can also be disposed onthe exterior of the casing. In this case, the sharpened end of theactuator would point inwardly to puncture the casing without puncturingthe membrane.

[0121] Another method for controlling the liquid flow rate is to createone or several extremely small apertures in an interior pouch that isdisposed within an exterior pouch having an outlet to restrict the flowof liquid from the interior pouch to the evaporator. Such apertures canbe formed in the interior pouch by using a laser or particle beam, forexample. Still another method is to mold or otherwise incorporate smallchannels of appropriate size and length into a piece of material such asplastic that is then sealed into the pouch which contains the liquid.Yet another method is to incorporate a valve in the liquid passagewaybetween the evaporator and liquid reservoir.

[0122] Referring back to FIGS. 1-3, refrigerant liquid 116 that is notimmediately vaporized can collect in the interstices of a wickingmaterial disposed in the evaporator 108. The wicking material isconfigured to draw and maintain a desired amount of liquid forvaporization. Thus, the wicking material should have a pore size that issufficiently large to permit capillary action to draw the liquid intothe pores. Further, the wicking material should be configured to absorbany vaporized liquid that recondenses. Preferred wicking materialsinclude hydrophilic materials such as microporous metals, porousplastics such as polyethylene and polypropylene, cellulose products(e.g., tissue paper) and other hydroscopic materials.

[0123] With the liquid to gas phase change, the liquid removes heat fromits surroundings via a cooling surface 120 that is equal to the latentheat of vaporization of the liquid. It will be appreciated that thecooling surface 120 can include fins or a similar structure to increasesurface area and enhance the cooling efficiency of the device.

[0124] The vaporized liquid then passes through the vapor passageway 104to be absorbed in the absorber 102. An optional vapor permeable membrane106 can be provided to prevent liquid from migrating to the absorber102. Examples of suitable vapor permeable membrane materials includevarious porous films such as TYVEK polyethylene films (E. I. duPontdeNemours Corporation, Wilmington, Del.), GORETEX films (W. L. Gore andAssociates, Newark, Del.), hydrophilic dense polyurethane films andporous hydrophobic polyurethane films such as those supplied by Porvair(Porvair plc., Norfolk, United Kingdom). The membrane can also have ahydrophilic coating such as SCOTCHGUARD (3M Company).

[0125] To ensure that the sorption cooling device operates for asuitable period of time, it is important to control the rate ofevaporation in the evaporator. If the liquid evaporates too quickly, thedevice will lose its ability to cool over an extended period of time.One way of controlling the rate of evaporation is to restrict the flowof vapor through the vapor passageway. For example, the vapor passagewaycould be provided with microchannels adapted to restrict the flow ofvapor through the vapor passageway. Further, a vapor-permeable membranehaving a specified pore size or permeability, as is discussed above, canbe provided in the vapor passageway.

[0126] In one embodiment of the present invention, the vapor passagewayincludes a thermally insulating material which is either porous or hasapertures formed in the material to allow vapor flow from the evaporatorto the absorber while reducing the heat flux from the absorber back tothe evaporator. The vacuum conditions under which the sorption coolingdevice is packaged advantageously enhances the high efficiency of thethermal insulation due to the Knudsen effect. That is, there is areduction in thermal conductivity that occurs when the mean free path ofa gas is equal to or greater than the pore size of the insulation. Thethermally insulating material preferably has a thermal-resistance at apressure of about 4 mbar (3 torr) of at least about 2.8 K·m²W, morepreferably at least about 4 K·m²/W and even more preferably at leastabout 6.5 K·m²/W. Further, the thermally insulating material preferablyhas a vapor transport rate of at least about 50 g/m²·hr at oneatmosphere of pressure. Due to the high insulative value of thethermally insulating material defining the vapor passageway, theevaporator and the absorber can be disposed in close proximity,separated only by the vapor. passageway, to give short vapor transferdistances.

[0127] An example of a vapor passageway that is useful in accordancewith the present invention and corresponds to the vapor passageway 104(FIGS. 1-3) is illustrated in FIGS. 13 and 14. The vapor passageway 1300is fabricated from thermally insulative material 1302 that includesapertures 1304 extending through the thermally insulative material 1302.The apertures 1304 provide the means by which vapor from an evaporatorcan pass through to an absorber. The apertures 1304 can be formed in thethermally insulative material by any common technique including drillingor punching, such as by punching with an array of heated nails.

[0128] As is illustrated in FIG. 3, the evaporator includes a liquidinlet, which is the point where the liquid exits the liquid conduit andenters the evaporator. It has been found that the region adjacent to theliquid inlet is susceptible to freezing thereby preventing furtherliquid flow between the evaporator and liquid reservoir. This isparticularly true if the liquid inlet is located too close to anyapertures 1304 in the thermally insulating material 1302. This isbecause the apertures 1304. are the means by which the evaporated liquidpasses to the absorber and are thus more likely to experience a decreasein temperature than the rest of the vapor passageway 1300. As a result,the. liquid inlet 1306 is preferably located near the perimeter (outeredge) of the evaporator (not illustrated) and the vapor passageway, asis illustrated in FIG. 13. This eliminates the need to pass the liquidconduit along the surface of the evaporator and vapor passageway whichwould increase the likelihood of freezing occurring in the liquidconduit. In the event that the liquid conduit passes over the surface ofthe evaporator, it is preferred that the liquid conduit be thermallyisolated from the cooling surface, such as with a layer of non-wovenglass fiber or a similar insulative-material.

[0129] Preferably, the concentration and/or size of apertures 1304 inthe thermally insulative material increases as the distance from theliquid inlet 1306 increases. This is to promote the movement of thevapor in a direction away from the liquid inlet 1306. Thus, theconcentration of apertures 1304 in the thermally insulative material1302 need not be uniform across the surface of the vapor passageway. Itis also important that no apertures 1304 are placed immediately adjacentto the liquid inlet, as noted above.

[0130] Another example of an embodiment of the vapor passageway isillustrated in FIG. 14. In this embodiment, the vapor passageway 1400includes, apertures 1404 incorporated in the thermally insulativematerial and vapor flow channels 1408 connecting individual apertures1404 for the purpose of directing the evaporated liquid towards theapertures 1404. This enables the vapor to exit the evaporator moreefficiently and increases the efficiency of the evaporator. While thechannels 1408 are depicted as being connected to the apertures 1404 in adirection perpendicular or parallel to the edges of the vapor passageway1400, it will be appreciated that the channels 1408 may be connected tothe apertures 1404 in any direction so long as the channels promote themovement of vapor to the apertures 1404. Moreover, the channels 1408 maybe any depth or shape just so long as their depth and shape promote themovement of the vapor. As with the previous embodiment, the channels1408 are preferably not located immediately adjacent to the liquidinlet.

[0131] Thermally insulating materials that are useful for the vaporpassageway according to this present invention include open-cell foams,such as polyurethanes, polystyrenes, or other foams as well porousinsulation including fiberglass or porous silica. Open-cell materialsare preferred to prevent outgassing when the cooling device isevacuated, as might occur with a closed cell material. As is discussedabove, microchannels can also be formed into the material to restrict orregulate the flow of vapor from the evaporator to the absorber Inaddition to the vapor passageway element described with respect to FIGS.13 and 14 and a vapor impermeable membrane, the vapor passageway caninclude other layers such as a layer of non-woven glass fiber, e.g, alayer of MANNIGLAS (Lydall, Inc., Manchester, Conn.) to enhance thevapor distribution.

[0132] The thickness of the vapor passageway is also an important factorthat influences properties of the sorption cooling device. If the vaporpassageway is too thick it will unnecessarily add to the cost, size andweight of the device. However, if the vapor passageway is too thin, itwill not serve the function of preventing thermal communication betweenthe absorber and the evaporator. Therefore, it is preferred that thethickness of the vapor passageway be sufficient to substantially preventthermal communication between the evaporator and absorber. The thicknessof the vapor passageway will depend on the properties of the thermallyinsulative material used in the device. It has been found that athickness of between about 0.5 cm and 5.0 cm is preferred, such as fromabout 2.5 cm to 5.0 cm when using a material such as an extrudedopen-celled polystyrene foam (e.g., INSTILL available from Dow ChemicalCompany, Midland, Mich.).

[0133] The diameter of the apertures in the thermally insulativematerial is another important factor for the sorption cooling device.Apertures that are too small will not allow the vapor to exit theevaporator at a sufficient rate. Apertures that are too big willincrease the thermal communication between the absorber and evaporatorthereby decreasing the thermal efficiency of the cooling unit.Therefore, it is preferred that the diameter of the apertures be suchthat it allows the vapor to flow from the evaporator to the absorber ata sufficiently high rate while allowing minimal thermal communicationbetween the absorber and evaporator. The preferred diameter of theapertures will depend on the type of thermally insulating material used,however it has been found that a preferred diameter is from about 0.8 mm({fraction (1/32)} of an inch) to about 6.4 mm (¼ of an inch), such asfrom about 1.6 mm ({fraction (1/16)} of an inch) to about 4.8 mm({fraction (3/16)} of an inch) when using a material such as INSTILL andwater as the refrigerant liquid. Preferably, the ratio of aperturelength to aperture diameter is from about 50:1 to about 4:1, morepreferably from about 25:1 to 4:1 particularly when using INSTILL as thethermally insulative material and water as the refrigerant liquid.Optionally, the average diameter of the apertures may increase as thedistance from the liquid inlet increases. It is also preferred that theopen area (i.e., area occupied by the apertures) is at least about 1percent, such as from about 5 percent to about 15 percent of the totalsurface area of the thermally insulative material.

[0134] Other means for restricting vapor flow through the vaporpassageway may be used, such as a bimetallic strip that is responsive totemperature changes. It will be appreciated that other means forrestricting vapor flow through the vapor passageway can be utilized.

[0135] The absorber includes an absorptive.material that is adapted toabsorb and retain vapor from the refrigerant liquid. That is, theabsorptive material must be capable of absorbing and/or adsorbing thevapor that is formed from the liquid. The absorptive material can becontained, for example, in a vapor permeable pouch. The mechanism bywhich the absorptive material functions can be a combination ofadsorption and absorption and as used herein, the terms absorb,absorptive, absorption and the like refer to the retention of liquid,regardless of the actual mechanism by which the liquid is retained. Theabsorptive material is preferably of such a nature and quantity as toabsorb all of the vaporized liquid.

[0136] When the refrigerant liquid includes water, the absorptivematerial can include a desiccant. to enhance absorption rates, thedesiccant can be activated prior to introduction into the absorber.Activation methods can include techniques such as heating the desiccantto remove moisture and/or any non-condensable gases. When the liquid iswater, the desiccant preferably absorbs at least about 20 percent of itsweight in liquid at a water pressure of 10 mbar (3.8 torr), morepreferably at least about 50 percent by weight at a pressure of 10 mbarand even more preferably at least about 75 percent by weight at pressureof 10 mbar.

[0137] The preferred desiccant will also absorb at least about 20percent of its weight in water at 10 percent relative humidity, and atleast 40 percent of its weight in water at 50 percent relative humidityand ambient temperature. More preferably, the desiccant will absorb atleast 40 percent of its weight at 10 percent relative humidity and 60percent of its weight at 50 percent relative humidity. Even morepreferably, the desiccant will absorb at least about 50 percent of itsweight at 10 relative percent humidity and at least about 80 percent ofits weight at 50 relative percent humidity.

[0138] Suitable desiccants include zeolites, barium oxide, activatedalumina, silica gel, glycerine, magnesium perchlorate, calcium sulfate,calcium oxide, activated carbon, calcium chloride, alumina gel, calciumhydride, phosphoric anhydride, phosphoric acid, potassium hydroxide,sodium sulfate and bentonite clay.

[0139] A particularly preferred desiccant in accordance with the presentinvention is a surface modified porous material. The porous material canbe a material such as activated carbon or silica. Preferably, the porousmaterial has a pore volume of at least about 0.8 cc/g and average poresize of from about 1 nm to about 100 nm. The surface modification caninclude impregnating the porous material with one or more absorbentssuch as a metal salt selected from the group consisting of calciumchloride, lithium chloride, lithium bromide, magnesium chloride, calciumnitrate, potassium fluoride and the like. Preferably, the metal salt isan environmentally benign salt, such as calcium chloride (CaCl₂). Theporous support material is preferably loaded with from about 20 to about80 weight percent of the metal salt and more preferably from about 40 toabout 60 weight percent of the metal salt and preferably is inpelletized form to provide vapor passageways among the desiccantparticles. Such desiccant compositions are described in detail in U.S.patent application Ser. No. 09/691,371, which is commonly-owned with thepresent application and which is incorporated herein by reference in itsentirety.

[0140]FIG. 15 illustrates the capacity of a preferred desiccantaccording to the present invention to absorb water at 24° C. compared tosilica gel at various vapor pressures. The surface modified desiccantillustrated in FIG. 15 is a surface modified carbon. The desiccant isformed from activated carbon having lithium chloride impregnated on theactivated carbon in a 1:1 mass ratio (i.e., 50 weight percent lithiumchloride). To fabricate the desiccant, lithium chloride salt isdissolved in water and dried activated carbon is added to the solution.The solution is adsorbed into the activated carbon and is then dried,leaving the activated carbon impregnated with the lithium chloride. Theprocess can be repeated to increase the loading of lithium chloride, ifnecessary.

[0141] It can be seen that this desiccant has substantially higher.waterabsorption ability as compared to the silica.gel. The use of desiccantcompositions having such high absorption capabilities enables thesorption cooling device to provide high cooling densities, therebyreducing the cost of shipping associated with the container as comparedto gel packs and similarly cooled containers.

[0142] The absorber can also include a monolith or a structure for theprovision of vapor pathways among the desiccant particles. For example,larger inert particles having a size that is at least 5 times to 10times the size of the desiccant particles can be dispersed among thedesiccant to provide such vapor pathways. Grid-like structures can alsobe disposed in the absorber to provide vapor pathways, such as metalscreen, glass fiber mesh, (e.g., MANNIGLAS, from Lydall, Inc.,Manchester, Conn.) or a plastic grid. The provision of vapor pathways inthe absorber can increase the absorption rate of the desiccant.

[0143] Another embodiment that is useful in accordance with the presentinvention is the use of high thermal conductivity material dispersedwithin the absorber. While the use of a desiccant is preferred for thefunction of absorbing vapor from the evaporator, generally suchdesiccants also have a relatively low thermal conductivity. As a result,the desiccant dissipates the generated heat at a rate that is lower thanthat of a higher thermal conductivity material. In order to decrease therate of heat dissipation in the absorber, a high thermal conductivitymaterial, can be added to the absorber. This will increase the thermaldissipation efficiency of the absorber and therefore the efficiency ofthe sorption cooling device.

[0144] According to this embodiment, the high thermal conductivitymaterial can be dispersed throughout the absorber in a manner such thatit maximizes its surface area contact with the desiccant whilesimultaneously allowing vapor to reach the desiccant. As a result,preferred high thermal conductivity materials include particulatematerials or fibrous materials, such as metal wools. The volumetricratio of desiccant to high thermal conductivity material is also animportant consideration and it has been found that between about 95 vol.% to 65 vol. % of the absorber (desiccant plus high thermal conductivitymaterial) should be occupied by the desiccant and between about 5 vol. %to 35 vol. % of the absorber volume should be occupied by the highthermal conductivity material. One preferred volumetric ratio ofdesiccant to high thermal conductivity material is from about 100:1 toabout 10:1.

[0145]FIG. 16 illustrates a cross-section of one embodiment of anabsorber that is useful in accordance with the present invention. Theabsorber 1600 contains a desiccant 1602 and a high thermal conductivityparticulate material 1604, sealed in a vapor permeable bag 1606. Vaporentering the absorber 1600 through the vapor permeable bag 1606 will beabsorbed by the desiccant 1602 thereby generating heat. The generatedheat will be passed via thermal conduction. to the particulate material1604 which, in turn, transfers the heat to the exterior of the absorber1600 thereby increasing the thermal efficiency of the absorber.

[0146]FIG. 17 illustrates a cross-section of another embodiment of theabsorber that is useful in accordance with the present invention. Theabsorber 1700 contains a desiccant 1702 and a fibrous material such asmetal wool 1704 enclosed in a vapor permeable bag 1706. Vapor enteringthe absorber 1700 from the vapor permeable bag 1706 will be. absorbed bythe desiccant 1702, thereby generating heat. The generated heat will bepassed via thermal conduction to the metal wool 1704 which, in turn,passes the heat to the exterior of the absorber 1700 thereby increasingthe thermal efficiency of the absorber. This structure can be formed bystretching the metal wool and pouring desiccant into the wool.

[0147] Preferably, the high thermal conductivity material will have athermal conductivity of at least about 1 W/m·k, and can be 20 W/m·k orhigher. Particulate materials that are useful as high thermalconductivity materials in accordance with this embodiment of the presentinvention include graphite, fibrous carbon, boron nitride (BN), alumina(Al₂O₃), copper, aluminum and mixtures thereof. Metal wools that areuseful in accordance with the current embodiment Include thosefabricated from copper, low-carbon steel, stainless steel, bronze,brass, aluminum, and alloys thereof and mixtures thereof.

[0148] It will also be appreciated that the absorber can be providedwith heat dissipating fins or similar structure on the top surface ofthe absorber to enhance the dissipation of heat from the absorber.

[0149] According to one embodiment of the present invention, a multiplestage sorption cooling device is provided to provide enhanced coolingcapacity. A multiple stage sorption cooling device is particularlyuseful when used in a container that must be maintained at very lowtemperatures, such as not greater than 0° C.

[0150] When liquid water is evaporated, there is an equilibrium vaporpressure of the water that is a function of the temperature of thewater. For different applications of a shipping container, differentliquid temperatures are needed to maintain the desired temperaturewithin the container. For example, water temperatures of less than 10°C. are desired for the 2° C. to 8° C. container and less than 0° C. fora frozen product. The equilibrium water vapor pressure for thesedifferent temperatures is illustrated in FIG. 5. As the temperatureincreases, the equilibrium vapor pressure also increases.

[0151] The capacity of a desiccant also depends upon the water vaporpressure. Specifically, as the vapor pressure increases (e.g., withincreasing temperature), the capacity of the desiccant to absorb wateralso increases. Thus, the capacity of the desiccant is also dependentupon the temperature of the water. This is illustrated by FIG. 18 forthree different temperatures. The practical result is that if a largetemperature difference is needed between the evaporator and thedesiccant (e.g, a very low evaporator temperature is needed), theabsorption capacity of the desiccant will be relatively low.

[0152] According to one embodiment of the present invention, a multiplestage sorption cooling device is utilized to address this problem. In amultiple stage sorption cooling device, two evaporators are used whereinthe first evaporator cools the product cavity and the second evaporatorcools the desiccant bed that is associated with the first evaporator.Thus, the temperature difference between the first evaporator and thehoftest desiccant bed is effectIvely doubled.

[0153] A schematic illustration of a multiple stage sorption coolingdevice in accordance with the present invention is illustrated in FIG.19. A first evaporator 1900 is utilized to provide cooling through acooling surface. A vapor passageway 1902 provides the vapor to a firstabsorber 1904 that includes a desiccant. As the first absorber 1904generates heat due to the absorption of vapor, a second cooling deviceincluding a evaporator 1906 is activated to cool the desiccant in thefirst absorber 1904. This enables the first absorber 1904 to capturemore vapor from the first evaporator 1900. A second vapor passageway1908 connects the second evaporator 1906 to a second absorber 1910.

[0154] To illustrate the increased efficiency of a multiple-stagecooling device, consider that 1 kg of water provides approximately 630W·hr of cooling. If the desiccant absorbs 1 kg of water per kg ofdesiccant and has a heat of adsorption that is 120% of the heat ofvaporization, a single stage sorption cooler that is designed for 10 Wof cooling would provide cooling for 63 hours, would weigh 2 kg andwould need to reject 12 W of heat. For a two-stage cooler with the samecooler capacity but running at twice the temperature difference betweenthe hot and cold sides, a total of 2.2 kg of water and 2.2 kg ofdesiccant would be required and the cooler would need to reject 14.4 Wof heat. Thus, an acceptably small increase in the mass of liquid anddesiccant can provide greatly increased cooling capacity and will beuseful for maintaining very low temperatures (e.g., below 0° C.) forextended periods of time.

[0155] It will be appreciated that the extension of the two-stage coolerillustrated in FIG. 19 to three or more stages is straightforward. Witheach extra stage, the amount of heat generated for a given amount ofcooling decreases and the mass and volume of both refrigerant andadsorbent increases.

[0156] The present invention is also directed to the incorporation of asorption cooling device into a shipping container to form atemperature-controlled shipping container. The foregoing descriptionillustrates certain preferred designs for the sorption cooling device,although the shipping containers of the present invention are notlimited thereto. The following description illustrates various examplesof temperature-controlled shipping containers according to the presentinvention. It will be appreciated that, although the present inventionis described with reference to these exemplary embodiments, the presentinvention is not limited to these particular embodiments.

[0157] Generally, the cooled shipping containers according to thepresent invention include a product cavity and a sorption coolingdevice, wherein the evaporator of the sorption cooling device is adaptedto cool the product cavity. Preferably, the heat generated in theabsorber is dissipated outside of the product cavity to maximize thecooling time available.

[0158] For example, a sorption cooling device incorporated into ashipping container in accordance with the present invention isillustrated in FIG. 20. Although illustrated as a substantiallyrectangular-shaped box, it will be appreciated that other containerconfigurations can also be utilized such as cylindrical containers andthe like. The temperature-controlled shipping container 2000 illustratedin FIG. 20 includes a sorption cooling device substantially as describedwith respect to FIGS. 1 and 2. The cooling surface 2020 of theevaporator 2008 is in thermal communication with the product cavity2030. The product 2032 is disposed within the cavity 2030 that isdefined by the top, bottom and side walls of an insulative insert 2034.In a preferred embodiment, the insulated walls defining the productcavity preferably have a thermal resistance of at least about 1 K·m²/Wand more preferably at least about 2 K·m²NV. However, it will beappreciated that such highly insulative walls may not be necessary forall applications of the present invention.

[0159] If desired, the insulative insert 2034 can be placed in anexternal container 2036, such as a corrugated cardboard box. Theabsorber 2022, which generates heat as liquid is absorbed, can bedisposed in thermal communication with the exterior of the externalcontainer 2036 such that heat is dissipated to the external environment.Alternatively, the absorber could be located outside of the insulativeinsert 2034 and within the external container 2036. If the absorber 2022is disposed within the external container 2036, venting means such asslots or perforations can be provided in the external container 2036 toassist in the dissipation of heat. Further, it is preferred that theabsorber 2022 is not in direct contact with the top of the externalcontainer 2036, as this would restrict heat dissipation from theabsorber. The external container can be provided with only two top flaps(as opposed to four flaps) on the side adjacent to the absorber todecrease the thickness and enhance heat dissipation. In any event, it ispreferred that the heat generated at the absorber 2022 is thermallyisolated from the product cavity 2030 so that the product cavity 2030 isable to maintain a sufficiently cool temperature for a sufficient lengthof time. Channels or other protrusions 2040 can also be provided withinthe product cavity to enhance circulation of the cooled air.

[0160] A mechanism can also be provided to indicate to the user that theactivated cooling device is operational. For example, a strip ofthermochromic ink 2038 can be disposed on the absorber or the evaporatorwhereby the ink changes color in response to a temperature change.Further, a rigid plate (e.g., a fiberglass, plastic, cardboard,chipboard or metal plate) can be disposed over the absorber to preventaccidental puncturing of the cooling device before or during use of theshipping container.

[0161] The preferred material for the insulated walls will depend uponthe application of the shipping container, such as the relative value ofthe products being shipped and the cooling requirements associated withthe product. In one embodiment, the insulated wall material has athermal conductivity of not greater than about 0.05 W/m·k, such as notgreater than about 0.04 W/m·k. Table 2 summarizes the properties of fouravailable materials: corrugated cardboard; expanded polystyrene (EPS);polyurethane; and vacuum insulated panels (VIPs). TABLE 2 Examples ofInsulative Materials Thermal Conductivity Material (W/m · K)Recyclability Formability Relative Cost Corrugated ˜0.05 High Yes LowCardboard EPS 0.035 Moderate Yes Low Polyurethane 0.025 Difficult YesMedium VIPs <0.006 Varies No Very High

[0162] For example, the insulated container and/or insert 2034 caninclude EPS as the sidewall material where the product 2032 is arelatively low-value commodity that is sensitive to increased costs. EPShas the advantage that it has a low-cost and is easily formed into avariety of shapes. However, to ensure sufficient insulation, arelatively thick amount of EPS is typically used. Further, there areenvironmental concerns with respect to the use of EPS.

[0163] VIPs have a very low thermal conductivity and therefore can beutilized in thinner sections than, for example, EPS. However, VIPs havea relatively high cost and would typically be used for high valuecommodities such as pharmaceuticals and medical specimens.

[0164] In addition, other insulative materials can be used includingexpanded polyethylene, expanded polypropylene, fiberboard andnon-corrugated cardboard. Gas filled insulative materials can also beused wherein a gas impermeable pouch is filled with an inert gas toprovide thermal insulation and to isolate the product. Examples of suchgas filled insulative materials are described in U.S. Pat. No. 6,341,475by Weder, U.S. Pat. No. 6,250,467 by Weder and U.S. Pat. No. 5,272,856by Pharo, each of which are incorporated herein by reference in itsentirety.

[0165] It will be appreciated that combinations of two or more insulatedmaterials can also be utilized. For example, VIPs could be utilized inthe thin areas of the cargo area with EPS at the opposite sides. FIG. 21illustrates a cross-sectional view of an insulated shipping containerinsert in accordance with an embodiment of the present of the presentinvention. The insulated shipping container insert 2100 includes vacuuminsulation panels 2102 and 2104 on the opposite sides of the insert,thereby maximizing the volume of space in the product cavity 2112. Thebottom insulator 2106 is fabricated from expanded polystyrene. The topinsulator 2108 is also fabricated from expanded polystyrene and includesa sorption cooling device 2110 to maintain a reduced temperature withinthe product cavity 2112.

[0166] According to one embodiment of the present invention, thesorption cooling device is disposable. That is, the sorption coolingdevice can be adapted to be used and then thrown away. Alternatively,the sorption cooling device can be partially or wholly recyclable. Inorder to recycle the sorption cooling device, the desiccant in theabsorber must be regenerated or replaced. Regeneration of the desiccantentails removing liquid from the desiccant by either heating thedesiccant, subjecting the desiccant to a vacuum or both. Further,additional refrigerant liquid must be provided to the sorption coolingdevice for subsequent use.

[0167] The desiccant can be regenerated either by removing the desiccantfrom the device or by regenerating the desiccant in-situ. For example,the entire sorption cooling device can be returned to the manufacturerwhere it is dismantled and the desiccant is removed and regenerated foruse in new cooling devices. Alternatively, the absorber can be designedas a removable piece of the sorption device. This piece would then bereturned and the desiccant removed and regenerated as described above.Regenerated desiccant can then be placed in new desiccant packs whichcan be packaged and placed into existing devices. According to yet afurther embodiment, the absorber can be packaged, such as in a rigidcontainer, and can be regenerated in-situ by opening a valve in theabsorber and placing the entire absorber in either an oven or a vacuum.Also, an integral heating unit could be provided with the absorberwhereby the heating unit can be activated to regenerate the desiccantin-situ.

[0168]FIG. 22 illustrates yet another embodiment of the presentinvention wherein the cooling capacity of the cooling device is enhancedby utilizing two absorbers. Specifically, FIG. 22 illustrates a shippingcontainer 2200 which includes a sorption cooling device including anevaporator 2202 and absorbers 2204 and 2206. The absorbers 2204 and 2206are connected to the evaporator 2202 by vapor passageways 2208 and 2210.

[0169] The evaporator is placed within a cavity defined by an insulatedinsert 2212. The absorbers 2204 and 2206 are placed on the externalportion of the insulated insert 2212. The entire insert can optionallybe placed in an external container 2214 for shipment, such as acorrugated cardboard box. As is discussed above, the external box can beprovided with venting means to assist in the dissipation of heat fromthe absorbers 2204 and 2206.

[0170]FIG. 23 illustrates yet another embodiment of a sorption coolingdevice and shipping container according to the present invention. Thesorption cooling device 2300 is a flat design useful for cooling smallpackages having a high aspect ratio. The liquid reservoir 2310 provideswater through a liquid conduit 2316 to an evaporator 2308. The watervapor then passes through vapor passageway 2304 to the absorber 2302.The entire assembly can be sealed in a vapor impermeable film, such as ametallized polyester film. In use, the absorber 2302 is thermallyisolated from the evaporator 2308 and the item to be cooled ispositioned adjacent to the large cooling surface of the evaporator 2308.The opposite surface of the evaporator 2308 can be insulated to maximizethe cooling affect. The cooling device 2300 is then placed into ashipping container 2312 with the product adjacent to the evaporator 2308and thermally isolated from absorber 2302, such as with a piece ofinsulation (not illustrated).

[0171]FIG. 24 illustrates a temperature-controlled shipping container2400 that is similar to the container illustrated in FIG. 20, whereintwo sorption cooling devices 2402 and 2404 are utilized to increase thetotal cooling capacity. Multiple cooling devices can be utilized tofurther decrease the temperature within the product cavity and/or can beused to increase the time over which cooling can be provided to theproduct cavity. The cooling devices can be activated simultaneously todecrease the temperature in the cavity or the devices can be activatedsequentially to increase the cooling time.

[0172]FIG. 25 illustrates a perspective view of yet another embodimentof the present invention wherein the shipping container 2500 includes abottom container portion 2502 that defines a cavity and is adapted tocontain a product within the cavity. The container includes a topportion 2504 that combines with the bottom portion 2502 and forms thetop wall of the container 2500. The top portion can be freely removablefrom the bottom portion 2502 or can be hinged on the bottom portion2502. A sorption cooling device 2506 is disposed in the top portion 2504and is adapted to provide cooling to the interior of the container. 2500Preferably, the sorption cooling device 2506 is disposed such that theabsorber portion is substantially planar with the top surface of the topportion 2504. The sorption cooling device 2506 can be provided to theuser separate from the container wherein the cooling device is insertedinto the container just prior to use.

[0173] A similar embodiment is illustrated in FIG. 26. In thisembodiment, the top portion 2604 includes a plurality of perforatedcut-outs, e.g., cut-outs 2608 and 2610. The cut-outs are adapted toreceive and support a sorption cooling device, such as cooling devices2612 and 2614 in the top portion of the container. In this way, anynumber of cooling devices (e.g., from 1 to 4) can be selected dependingon the anticipated cooling demand for the container, without the addedcosts associated with containers having different configurations. A usercan simply calculate the cooling demand and select the number of coolingdevices accordingly.

[0174]FIG. 27 illustrates an embodiment of the present invention whereina flat and flexible cooling device is disposed in a cylindrical shippingcontainer having one continuous sidewall. The cooling device includes anabsorber portion 2704 that is disposed to face the exterior of thecontainer and an evaporative portion 2702 (i.e., a cooling surface) thatis disposed adjacent to the central portion of the container to cool aproduct disposed therein.

[0175] It will also be appreciated that the sorption cooling devicesaccording to the present invention can also be disposed in othercontainers, such as in flat mailing envelopes. For example, a sorptioncooling device can be disposed in an envelope that is adapted to carry atemperature sensitive product. The product can then be shipped to aconsumer or the consumer can purchase the product and take the producthome in the temperature controlled envelope.

[0176] Table 3 illustrates the cooling performance of a sorption coolingdevice in accordance with the present invention as compared to the priorart. TABLE 3 Cooling Options Nominal Cooling Temperature Energy/MassEnergy/Volume Mechanism (° C.) (W · hr/kg) (kW · hr/m³) Ice/Gel Packs* 092 92 Dry Ice* −78 208 175 Liquid Nitrogen* −196 55 44 Phase ChangeVariable 30-70 30-60 Materials* Sorption Cooling −20 to +20 180-315145-250

[0177] For optimal cooling performance while maintaining reasonable massand the volume for reduced shipping costs, is desirable that the energydensity values (energy/mass and energy/volume) be as high as possible.As is illustrated in Table 3, although ice/gel packs have a relativelylow cost, the energy density values are relatively low. Therefore, alarge mass and volume of the ice/gel packs is required to cool theshipping container.

[0178] Likewise, liquid nitrogen and phase change materials also havevery low energy densities. Although dry ice has a higher energy density,dry ice is considered hazardous and is not an acceptable material forair freight.

[0179] Absorption cooling in accordance with the present inventionprovides a useful range of cooling, from −20° C. to +20° C., and has ahigh energy density. The energy density values listed for the sorptioncooler are based upon a desiccant absorption capacity of 50 weightpercent to 200 weight percent and a total mass or volume based on thesum of the liquid and the desiccant. The actual value will depend on thedesiccant capacity and the packaging configuration. Preferably, the massenergy density is at least about 100 W·hr/kg, more preferably at leastabout 180 W·hr/kg. Further, the volume energy density is at least about80 kW·hr/m³ and more preferably is at least about 150 kW·hr/m³. In someinstances, it may be desirable to cool the cooling device, e.g., in arefrigerator before utilization to provide increased cooling capacity.

[0180] The temperature controlled shipping containers in accordance withthe present invention can be utilized to transport a number of productswhile maintaining the temperature of the products below or within aspecified temperature range. Products that cna advantageously betransported in accordance with the present invention include, but arenot limited to heat-sensitive products such as: pharmaceuticals such asprotein-based pharmaceuticals, vaccines and insulin; food and beverageproducts such as confectionary products; floral products; biologicalsamples such as blood, tissue, organs, eggs and semen; semiconductorchemicals; paints; electronics; photographic film; adhesives; andcosmetics.

[0181] The temperature-controlled shipping containers of the presentinvention can maintain a reduced temperature within the product cavityfor an extended period of time. In one embodiment, the product cavitycan be maintained at a temperature of not greater than about 8° C. forat least about 24 hours, more preferably at least about 48 hours andeven more preferably at least about 72 hours. Shipping containers can befabricated to meet virtually any cooling demand for a period of time ofup to 100 hours or longer, if necessary.

EXAMPLES

[0182] Shipping Containers Prototype temperature-controlled shippingcontainers according to the invention were fabricated. While thetemperature-controlled shipping containers of the present invention arenot considered to be restricted by size, two different size sorptioncooling devices were tested. “Size A” had dimensions of 7″×8″×1.5″ (178mm×203 mm×38 mm) and “Size B” had dimensions of 5″×6″×1.25″ (127 mm×152mm×32 mm).

[0183] The sorption cooling devices include layers of differentmaterials stacked on each other. These layers will be described in orderfrom the exterior face of the cooling device (i.e., the absorber) to theinterior face (i.e., the cooling surface of the evaporator)that facesthe internal cavity of the container.

[0184] A. Absorber

[0185] To form the absorber, a dessicant is contained by a porous bagsealed by an ACCU-SEAL 50 (Accu-Seal Corporation, San Diego, Calif.).The porous bag is constructed of a spun bonded polyethylene material(ReeMay, Old Hickory, Tenn.). The finished desiccant bag dimensions areabout 7″×8″ (178 mm×203 mm) for Size A cooler and 5″×6″ (127 mm×152 mm)for a Size B cooler, as measured from the inside of one seal to theinside of the opposite seal. The dessicant is uniformly distributedwithin the bag when the bag is laying flat. Size A utilized 80 grams ofdessicant while Size B utilized 25 grams of desiccant. The desiccant wasa surface modified desiccant consisting of lithium chloride (LiCl)dispersed on an activated carbon support in a 1:1 mass ratio. Tofabricate the desiccant, lithium chloride salt was dissolved in waterand dried activated carbon was added to the solution. The solution wasdried, leaving a composite desiccant of activated carbon impregnatedwith 50 wt. % lithium chloride.

[0186] B. Thermally Insulating Material (Vapor Passageway)

[0187] The vapor passageway of the sorption cooling device includedthree separate layers: a 1″ (25.4 mm) thick piece of INSTILL (anextruded open-cell polystyrene material available from Dow ChemicalCompany, Midland, Mich.) sandwiched between two layers of MANNIGLASS 60(a non-woven fiberglass available from Lydall, Inc. Manchester, Conn.).For a Size A cooler, the first MANNIGLASS layer and the INSTILL layerare cut to a size of 7″×8″ (178 mm×203 mm) and the second layer ofMANNIGLASS is cut to a size of 5″×6″ (127 mm×152 mm). The INSTILL isdrilled with a ⅛ ″ (3.2 mm) drill bit in a 5″×6″ (127 mm×152 mm) areacentered in the middle of the INSTILL layer, with a hole density ofabout 7 holes per square inch (about 1 hole per square centimeter). Fora Size B cooler, all three insulating pieces are cut to a size of 5″×6″(127 mm×152 mm). The INSTILL piece is drilled with a ⅛ ″ (3.2 mm) drillbit over the entire 5″×6″ area so that it has a hole density of about 7holes per square inch (about 1 hole per square centimeter).

[0188] C. Evaporator

[0189] A composite material consisting of an expandedtetrafluoroethylene (ETFE) fluorocarbon polymer (TEFLON, E.I. duPontdeNemours and Company, Wilmington Del.) laminated onto a spun bondedpolyethylene material was obtained from Tetratex, Feasterville, Pa. Thecomposite material had an average pore size of 1 μm and was in the formof a bag. For a Size A cooling device, the width of the bag is 8″ (203mm) and the length is at least 16″ (406 mm). For a Size B coolingdevice, the width of the bag is 5″ (127 mm) and the length is 6″ (152mm). The bag is sealed using an ACCU-SEAL 50 with the interior of thebag containing the wicking material. The wicking material is a KIMWIPEEX-L (Kimberly-Clark Corporation, Roswell, Ga.), a paper tissuemanufactured from 100 percent virgin wood fiber. The dimensions of thepaper tissue is 7″×8″ (178 mm×203 mm) for a Size A device and 5″×6″ (127mm×152 mm) for a Size B device.

[0190] D. Water Reservoir System

[0191] For a Size B device, the water reservoir system included a smallwater reservoir taped to the center of the wicking material. For a SizeA device, the water reservoir system included a small starter waterreservoir in a first pouch and a large water reservoir in a largersecond pouch. These will be described separately.

[0192] 1. Large Water Reservoir and Pouch

[0193] a. Water Reservoir

[0194] The water reservoir bag was fabricated from a plastic materialcut and sealed in the shape of a rectangle having a size of 4″×3″ (102mm×76 mm). The plastic is a polyester-polyethylene material availablefrom Rollprint Packaging Products, Addison, Ill. The plastic bag issealed on all four sides with little or no air in the sealed bag. Agraduated syringe with an 18 gauge needle is used to fill the bag. Acorner of the bag is punctured with the needle through one side of theplastic and the bag is filled with the water from the. syringe. The SizeA bag is filled with 40 milliliters of water. The plunger of the emptiedsyringe, with the needle still in the bag, is slowly pulled to extractany trapped air in the bag. With the needle still in the bag, thepuncture in the bag is placed on the ACCU-SEAL 50 so that the machineseals the bag closed. The needle is not removed from the bag until themachine is in the process of sealing the bag so that no water.leaksout.of the.puncture. Once the full bag is sealed, it is,very flexibleandthe bag must be resealed repeatedly to form a progressively smaller baguntil the full bag cannot be sealed to a smaller size. Any excess edgesformed from the sealing are trimmed with a ¼ ″ (6.4 mm) edge remainingand these edges are taped flat to the tightened bag. A 1″×¾″ (25.4mm×19.1 mm) puncturing device (described below) is taped to one face ofthe full reservoir ensuring that the tape does not cover the point ofthe puncturing device. This device is described more fully below.

[0195] b. Large Pouch with Filter

[0196] The large water reservoir was contained within a large triangularpouch having a 1 cm×1 cm filter at one end. The filter was cut from alarger piece of a 0.1 μm filter material (Micron Separations Inc.,Westboro, Mass.). The triangular pouch has dimensions of 7″ (178 mm)across the base and two equal 6″ (152 mm) sides. The filter was sealedwith an ACCU-SEAL 50 into one side of the narrow point of the triangularpouch. The large water reservoir was placed in the pouch near the base.To create channels to carry water from the punctured reservoir to thefilter, a plastic cord was used that is approximately 8″ (203 mm) inlength. To create the channels, the cord was doubled and one end of thecord is placed under the filter. The doubled cord reaches the reservoirand is in contact with the point of the puncturing device. Finally, thelarge pouch was completed by sealing with the ACCU-SEAL 50 across thebase.

[0197] 2. Starter Water Reservoir and Pouch

[0198] a. Starter Water Reservoir

[0199] The starter bag was constructed of the same plastic material andin an identical manner as the large reservoir described above. However,the initial dimensions of the plastic bag are 1½″×2″ (38 mm×51 mm). Thisstarter bag contains 5 milliliters of a solution containing 10 wt. %NaCl and 90 wt. % water. As described earlier, the bag was sealed sothat it is tight. A puncturing device was attached to one face of thereservoir with tape.

[0200] b. Starter Water Reservoir Pouch

[0201] The starter water reservoir pouch was constructed of the sameplastic material as the reservoirs and pouches described above. However,the shape of the starter pouch is roughly T-shaped. The upper bar of theT-shape is approximately 2″ (51 mm) in width and 4″ (102 mm) in lengthwhile the leg of the T-shape is approximately ½″ (13 mm) in width and 8″(203 mm) in length. The starter pouch has a 1 mm hole punctured throughone side of the plastic about ¼″ (6.4 mm) from the bottom of theT-shape. A 14″ (356 mm) long cord was doubled and one end placed so thatit surrounds the hole at the bottom of the pouch. The doubled cordreaches the starter reservoir and is in contact with the point of thepuncturing device.

[0202] 3. Puncturing Device

[0203] A puncturing device is made from a 0.034″ (0.86 mm) thickaluminum sheet. It is cut in a teardrop shape approximately 1″×¾″ (25.4mm×19.1 mm) for the large water reservoir and approximately ¹2″×¼″ (12.7mm×6.4 mm) for the small water reservoir. The point of the teardrop issharp and is slightly bent so that when the device is taped to thereservoir, the point presses into the reservoir.

[0204] 4. Attaching Water Reservoir System to Evaporator (Size A only)

[0205] The starter pouch is attached so that the end with a holepunctured in it is centered on the wicking material. The starter pouchis attached with a minimum of tape. The filter end of the larger pouchis attached to the 8″ (203 mm) side of the wicking materialapproximately ½″ (12.7 mm) from the edge. Both the starter pouch and thelarger pouch extend in the same direction over the same edge of thewicking material. The pouches and attached wick are placed inside theETFE composite bag. The wick lies flat in the composite ETFE bag and anywrinkles are removed. Once the pouches and the wicking material areplaced in the composite ETFE bag, the bag is sealed.

[0206] E. ASSEMBLY OF COOLING DEVICE

[0207] 1. Size B Cooling Device

[0208] From bottom to top, the cooling device is fabricated by stackingthe MANNIGLASS on top of the desiccant bag, followed by the INSTILLlayer and the remaining layer of MANNIGLASS.

[0209] The composite ETFE bag is laid on top with the water reservoirfacing out. The stacked components are placed into a plastic bag made ofthe polyester-polyethylene laminate material described above. This baghas a sufficient size to contain the entire component stack. The bag isthen evacuated to a pressure of 1.73 torr (2.3 mbar).

[0210] 2. Size A Cooling Device

[0211] From bottom to top, the cooling device is formed with thedesiccant bag first. Next, a layer of MANNIGLASS is laid on top of thedesiccant bag, followed by the INSTILL, followed by the remaining layerof MANNIGLASS.

[0212] The composite ETFE bag is laid on top of that with the waterreservoirs facing outwardly and the composite ETFE bag is arranged ontop of the insulation so that the wicking material inside the compositeETFE bag is directly over the insulation. The composite ETFE bag shouldextend over one end of the insulation.

[0213] The stacked components are placed into a plastic bag made of thepolyester-polyethylene laminate material described above. This bag is ofsufficient size to contain the stacked components. The bag is thenevacuated to a pressure of 1.73 torr (2.3 mbar).

[0214] F. SHIPPING CONTAINERS

[0215] The containers were constructed of pieces of an insulatingmaterial taped together to form four sides and a bottom. The coolingdevice to be tested is placed on the top of the container, therebyenclosing the shipping cavity.

[0216] 1. VIP Container

[0217] For illustrative purposes, a container was constructed of 1″thick vacuum insulation panels (VIPs), the dimensions of the five pieceswere: two pieces at 6″×6″ (152 mm×152 mm), two pieces at 7″×6″ (178mm×152 mm), and one piece at 7″×8″ (178 mm×203 mm). U.S. Pat. No.5,877,100 by Smith et al. provides details on how to assemble anindividual VIP and this patent is incorporated herein by reference inIts entirety.

[0218] The four sides of the container consist of the two 6″×6″ and thetwo 7″×6″ pieces with the 7″×8″ piece forming the bottom of the box. Thepieces are fitted together so that the four sides are perpendicular thebottom and the sides do not hang over the edges of the bottom. Tape isused to secure all pieces to each other and to cover any joints betweenpieces. The inside cavity of the finished container is 5″ wide×6″long×6″ deep (127 mm×152 mm×152 mm).

[0219] 2. EPS Container

[0220] A container constructed of 1″ thick EPS (expanded polystyrene)material was assembled in a similar manner as the VIP container, exceptthe dimensions of the pieces are as follows: two 6″×6″ (152 mm×152 mm),two 7″×6″ (178 mm×152 mm), two 9″×10″ (229 mm×254 mm), two 8″×6″ (203mm×152 mm) and two 9″×6″ (229 mm×152 mm). Before assembling thecontainer, all cut sides of the EPS are taped so that the foam edges donot crumble. The EPS container is double-walled on the sides and thebottom. The two 9″×10″ pieces are stacked to form the bottom of the boxand the inner wall consists of the two 6″×6″ and the two 7″×6″ piecesfitted together. The outer walls of the box consist of the two 8″×6″ andthe two 9″×6″ pieces that are fitted together around the inner walls.Tape is used to secure all pieces to each other and to cover any jointsbetween pieces. The inside cavity of the finished box is 5″ wide×6″long×6″ deep (127 mm×152 mm×152 mm).

[0221] To begin cooling, the water reservoir(s) is punctured and thecooling device is quickly placed onto the top of the containers. TheSize A cooling device is placed onto the open top of the container withthe desiccant facing outwardly. The Size B cooling device is pushed intothe container cavity until the desiccant is flush with the top of thesides of the container. For both sizes, the cooling device is secured tothe container so that all joints between the cooling device and thecontainer are covered with tape.

[0222] The performance of the cooling devices was tested by monitoringthe temperature as a function of time for the internal cavity of thecontainer near the evaporator, the external surface of the desiccant andthe room. Prior to every experiment, Omega Type K thermocouples (OmegaEngineering, Stamford, Conn.) were attached to the external surface ofthe desiccant and to the inside of the container so that the temperatureof the center of the internal cavity within the container is measured.The third thermocouple recorded the ambient temperature of the room inwhich the experiment was being conducted. Data measurements wererecorded every 30 seconds for Size B cooling devices and every 5 minutesfor Size A cooling devices, beginning about 10 seconds before the waterreservoir(s) was punctured. Measurement continued until the internal boxtemperature and the desiccant temperature were approximately equal.

Example 1

[0223] Cooling Device with Extended Cooling Time

[0224] Example 1 was a Size A cooling device with 400 grams of desiccantand 200 milliliters of water in the slow feed water reservoir. Thiscooling device also had two layers of wicking material, instead of one.The cooling device was tested in a VIP container and the results areillustrated in FIG. 28, which shows the ambient temperature, desiccanttemperature and internal base temperature as a function of time.

[0225] As is illustrated in FIG. 28, the temperature of the cavitydropped from about 26° C. to about 6° C. and the temperature did notrise above 10° C. for at least 48 hours.

Example 2

[0226] Effect of Starter Reservoir on Performance

[0227] Two Size A cooling devices (Examples 2A and 2B) were assembled sothat they were identical to each other except that Example 2A did nothave a starter liquid reservoir and Example 2B utilized a starterreservoir. Both were tested in VIP containers. The results for Example2A are illustrated in FIG. 29 and the results for Example 2B areillustrated in FIG. 30. It can be seen that the internal cavity ofExample 2,B exhibited a rapid drop to less than 5° C., whereas theinternal cavity of Example 2A dropped to slightly less than 10° C.,demonstrating the effectiveness of utilizing a starter liquid reservoir.

Example 3

[0228] EPS Container vs. VIP Container

[0229] Two identical Size A cooling devices were assembled. One (Example3A) was tested in an EPS container and the other (Example 3B) was testedin a VIP container. The results for Example 3B are illustrated in FIG.31 and the results for Example 3A are illustrated in FIG. 32.

[0230] As expected, the VIP container yielded a reduced internal cavitytemperature over a longer period of time due to the improved thermalinsulation properties of the VIPs.

Example 4

[0231] Effect of Different Size Containers

[0232] Two identical Size B cooling devices were assembled, however onewas tested in a VIP container as described above (Example 4A) withdimensions of 5″×6″×6″ (127 mm×152 mm×152 mm) and the other coolingdevice was tested in smaller sized VIP container (Example 4B). Thesmaller VIP container had dimensions of 1″ deep×5″ wide×6″ long (25.4mm×127 mm×152 mm) and was constructed using VIP panels ¼″ (6.4 mm)thick.

[0233] The results for Example 4A are illustrated in FIG. 33 and theresults for Example 4B are illustrated in FIG. 34. The container havinga reduced aspect ratio (Example 4B) maintained a reduced temperature fora longer period of time.

Example 5

[0234] Different Types of Desiccant

[0235] Two identical Size B cooling devices were assembled, but Example5A contained 25 grams of {fraction (1/16)}″ 13X Molecular Sieve (EMScience Company, Gibbstown, N.J.) and Example 5B (same as Example 4B)included the composite desiccant as described above. The results forExample 5A are illustrated in FIG. 35 and the results for Example 5B areillustrated in FIG. 34. The composite desiccant maintained a reducedtemperature for a longer period of time.

Example 6

[0236] Effect of Desiccant Type on Cooling Device Performance

[0237] Two substantially identical temperature-controlled shippingcontainers were assembled, but Example 6A contained a zeolite desiccant(Aldrich, Molecular Sieve 13X) and Example 6B contained a compositedesiccant as described above. The results are illustrated in FIG. 36(Example 6B) and FIG. 37 (Example 6A). While both desiccant materialsprovided adequate cooling, the composite desiccant provided somewhatbetter results.

Example 7

[0238] Varying Internal Pressure of Cooling Devices

[0239] In a further set of Examples, three substantially identicalcooling devices were assembled, except that each cooling device wasevacuated to a different internal pressure, namely 1.7 torr, 10 torr and40 torr. All three cooling devices were assembled substantially inaccordance with the foregoing description and were placed insubstantially identical shipping containers. The results are illustratedin FIG. 38 (1.7 torr), FIG. 39 (10 torr) and FIG. 40 (40 torr). The bestresults over an extended period of time were obtained at the lowestpressures.

Example 8

[0240] Varying Desiccant Particle Size

[0241] Two substantially identical temperature-controlled shippingcontainers were assembled, but the cooling device of Example 8A included5×10 mesh pellets of a desiccant formed from LiCl on carbon(MeadWestvaco NUCHAR BAX 1500) and Example 8B included a desiccant madefrom 10×25 mesh pellets of a desiccant formed from LiCl on carbon(MeadWestvaco NUCHAR WVA 1500) ground to a particle size of 150 μm to850 μm. The results are illustrated in FIG. 41 (Example 8A) and FIG. 42(Example 8B). The best results were obtained with the desiccant having alarger particle size.

Example 9

[0242] Increasing Metal Salt in Desiccant

[0243] Two substantially identical temperature-controlled shippingcontainers were assembled, but Example 9A comprised an absorber with acomposite desiccant including 60 vol. % LiCl and Example 9B comprised anabsorber with a composite desiccant including 50 vol. % LiCl. Thecontainers were tested and the results are illustrated in FIG. 43(Example 9A)-and FIG. 44 (Example 9B). It can be seen that thetemperature-controlled shipping container with the 60 vol. % LiCldesiccant (Example 9A) remained below 15° C. for at least 50 hours,while the temperature-controlled shipping container remained below 15°C. for about 42 hours. Increasing the amount of LiCl increased thelongevity of the shipping container.

Example 10

[0244] Addition of Graphite to Desiccant

[0245] Two substantially identical temperature-controlled shippingcontainers were assembled, but Example 10A comprised an absorber with80% weight desiccant and 20% weight Asbury Graphite (Asbury Carbons,Inc., Asbury, N.J.) as a thermally conductive material and Example 10Bcomprised an absorber with the same desiccant, but no graphite. Theresults are illustrated in FIG. 45 (Example 10B) and FIG. 46 (Example10A). The cooling device with the graphite in the absorber had a longeruseful cooling life than the cooling device without a thermallyconductive material.

Example 11

[0246] Varying Thickness of Thermally Insulating Material

[0247] Three substantially temperature-controlled shipping containerswere assembled. Example 11A included a vapor passageway thickness(INSTILL) of 1″ (25.4 mm), Example 11B included a vaporpassagewaythickness (INSTILL) of ½″ (38.1 mm) and Example 11° C. included a vaporpassageway thickness (INSTILL) of 2″ (51 mm). The results areillustrated in FIG. 47 (Example 11A), FIG. 48 (Example 11B) and FIG. 49(Example 11° C.). The best results were obtained with increased vaporpassageway thickness.

[0248] While various embodiments of the present invention have beendescribed in detail, is apparent that modifications and adaptations ofthose embodiments will occur to those skilled in the art. However, is tobe expressly understood that such modifications and adaptations arewithin the spirit and scope of present invention.

1-70. (Cancelled).
 71. A sorption cooling device, comprising: a) anevaporator for providing cooling; b) an absorber adapted to absorb vaporformed in said evaporator; and c) a vapor passageway adapted to permitvapor flow from said evaporator to said absorber, wherein said vaporpassageway comprises a thermally insulating material having a thermalresistance of at least about 2.8 K·M²/W at a pressure of about 4 mbar.72. A sorption cooling device as recited in claim 71, wherein saidthermally insulating material comprises open-cell foam material.
 73. Asorption cooling device as recited in claim 71, wherein said thermallyinsulating material comprises polyurethane open-cell foam.
 74. Asorption cooling device as recited in claim 71, wherein said thermallyinsulating material comprises polystyrene open-cell foam.
 75. A sorptioncooling device as recited in claim 71, wherein said thermally insulatingmaterial comprises a material selected from the group consisting offiberglass and porous silica.
 76. A sorption cooling device as recitedin claim 71, wherein said vapor passageway comprises said thermallyinsulating material having a plurality of apertures therethrough toprovide vapor communication between said evaporator and said absorber.77. A sorption cooling device as recited in claim 76, wherein none ofsaid apertures are immediately adjacent to said liquid inlet.
 78. Asorption cooling device as recited in claim 76, wherein the number ofsaid apertures in said thermally insulative material increases as thedistance between said liquid inlet and said apertures increases and noapertures are located immediately adjacent to said liquid inlet.
 79. Asorption cooling device as recited in claim 76, wherein said aperturesare substantially cylindrical.
 80. A sorption cooling device as recitedin claim 76, wherein said apertures are substantially cylindrical andwherein the diameter of said cylindrical apertures is from about 0.8 mmto about 6.4 mm.
 81. A sorption cooling device as recited in claim 76,wherein said apertures are substantially cylindrical and wherein theratio of the length of said apertures to the cylindrical diameter ofsaid apertures is from about 50:1 to about 4:1.
 82. A sorption coolingdevice as recited in claim 71, wherein said thermally insulatingmaterial has a thermal resistance of at least about 4 K·m M2N at apressure of about 4 mbar.
 83. A sorption cooling device as recited inclaim 71, wherein said thermally insulating material has a thermalresistance of at least about 6.5 K·m² W.
 84. A sorption cooling deviceas recited in claim 71, wherein said evaporator comprises a planarevaporative surface and further comprising a liquid inlet is disposed ona perimeter of said planar evaporative surface.
 85. A sorption coolingdevice as recited in claim 71, wherein said thermally insulativematerial comprises a plurality of apertures and the concentration ofsaid apertures in said thermally insulative material is substantiallynon-uniform.
 86. A sorption cooling device as recited in claim 85,wherein the concentration of apertures in said thermally insulativematerial increases as the distance from said liquid inlet increases. 87.A sorption cooling device as recited in claim 71, wherein said thermallyinsulative material comprises a plurality of apertures and the diameterof apertures in said thermally insulative material increases as thedistance from said liquid inlet increases.
 88. A temperature-controlledshipping container incorporating a sorption cooling device as recited inclaim
 71. 89-100. (Cancelled)